[ovs-dev] [OVN Patch v14 1/3] ovn-libs: Add support for parallel processing

Numan Siddique numans at ovn.org
Thu Feb 25 14:29:47 UTC 2021


On Thu, Feb 25, 2021 at 7:33 PM Anton Ivanov
<anton.ivanov at cambridgegreys.com> wrote:
>
> Found the most likely culprit.
>
> This is similar to this: https://bugzilla.redhat.com/show_bug.cgi?id=663584
> this: https://bugzilla.redhat.com/show_bug.cgi?id=1554955
> and god knows how many others.
>
> Selinux is "securing" your semaphores.

I disabled selinux (permissive) and I still see the same behavior


>
> A.
>
> On 25/02/2021 13:27, Anton Ivanov wrote:
> >
> > On 25/02/2021 12:41, Numan Siddique wrote:
> >> On Fri, Feb 12, 2021 at 8:20 PM Anton Ivanov
> >> <anton.ivanov at cambridgegreys.com> wrote:
> >>> This adds a set of functions and macros intended to process
> >>> hashes in parallel.
> >>>
> >>> The principles of operation are documented in the fasthmap.h
> >>>
> >>> If these one day go into the OVS tree, the OVS tree versions
> >>> would be used in preference.
> >>>
> >>> Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
> >> Hi Anton,
> >>
> >> I still see problems with this patch set.
> >>
> >> If I apply the first 2 patches and run the tests, most of the test
> >> cases fail or hang.
> >>
> >> When configured with gcc and address sanitizer,  the test case fails -
> >> 45. ovn.at:2970: 45. ovn -- 2 HVs, 2 LS, switching between multiple
> >> localnet ports with same tags (ovn.at:2970): FAILED
> >> (ovs-macros.at:219) and I see the below in the testsuite.log
> >>
> >> *********
> >> clean up OVN
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovsdb-server.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovsdb-server exit
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded immediately
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovsdb-server.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovsdb-server exit
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded immediately
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovn-northd.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovn-northd exit
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded after 1 seconds
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovn-northd.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovn-northd exit
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded quickly
> >>
> >> main: clean up vswitch
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovs-vswitchd.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovs-vswitchd exit --cleanup
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded quickly
> >> ../../tests/ovn.at:3091: test -e $OVS_RUNDIR/ovsdb-server.pid
> >> ../../tests/ovn.at:3091: ovs-appctl --timeout=10 -t ovsdb-server exit
> >> ovn.at:3091: waiting while kill -0 $TMPPID 2>/dev/null...
> >> ovn.at:3091: wait succeeded immediately
> >> Address Sanitizer reported errors in: asan.2986645
> >> =================================================================
> >> ==2986645==ERROR: AddressSanitizer: SEGV on unknown address
> >> 0x14f45be57000 (pc 0x14f45f424212 bp 0x000000000000 sp 0x14f45b1fda80
> >> T2)
> >> ==2986645==The signal is caused by a READ memory access.
> >> ../../tests/ovs-macros.at:219: hard failure
> >> 45. ovn.at:2970: 45. ovn -- 2 HVs, 2 LS, switching between multiple
> >> localnet ports with same tags (ovn.at:2970): FAILED
> >> (ovs-macros.at:219)
> >>
> >> ******
> >>
> >> The same is observed for many test cases.
> >>
> >> When I configure clang and run the tests, all the tests pass, but I
> >> see lot of coredumps.
> >> I think I had reported this earlier too.
> >
> > I have absolutely no idea how you get this. Seriously.
> >
> > I have been unable to reproduce this
> >
> > The only thing that comes to mind is to "fuzz" the semaphore creation and introduce random failures there to see if the error logic works. I can't see any logical problems in it via code inspection.
> >
> >>
> >> Here is the backtrace
> >> -----
> >> #0  0x00001528ad37a212 in __new_sem_wait_slow.constprop.0 () from
> >> /lib64/libpthread.so.0
> >> [Current thread is 1 (Thread 0x1528ac732640 (LWP 2907214))]
> >> Missing separate debuginfos, use: dnf debuginfo-install
> >> glibc-2.32-3.fc33.x86_64 libcap-ng-0.8-1.fc33.x86_64
> >> libevent-2.1.8-10.fc33.x86_64 openssl-libs-1.1.1i-1.fc33.x86_64
> >> python3-libs-3.9.1-2.fc33.x86_64 unbound-libs-1.10.1-4.fc33.x86_64
> >> zlib-1.2.11-23.fc33.x86_64
> >> (gdb) bt
> >> #0  0x00001528ad37a212 in __new_sem_wait_slow.constprop.0 () from
> >> /lib64/libpthread.so.0
> >> #1  0x0000000000421d84 in wait_for_work (control=0xf5c0e0) at
> >> ../lib/ovn-parallel-hmap.h:193
> >> #2  build_lflows_thread (arg=0xf5c0e0) at ../northd/ovn-northd.c:11807
> >> #3  0x000000000049c8b2 in ovsthread_wrapper (aux_=<optimized out>) at
> >> ../lib/ovs-thread.c:383
> >> #4  0x00001528ad3713f9 in start_thread () from /lib64/libpthread.so.0
> >> #5  0x00001528ad00e903 in clone () from /lib64/libc.so.6
> >> ----
> >>
> >>
> >> I'm sorry but something is not right. Instead of using semaphores, why
> >> can't we use
> >> 'struct latch' for each worker and use it to synchronize between the main thread
> >> and the workers ?
> >
> > We can't because this will conflict with the main poll loop.
> >
> > You need to rewrite the entire northd processing logic and the IO logic to use latch here. Or establish parallel logic - part of the joy of using "thead once" to do poll magic.
> >
> > None of these are a realistic option. I'd rather try to understand exactly what happens on your setup and what makes a sem_open() fail and why that is not handled properly by the error checking code.
> >
> > Can you send the results of "sysctl kernel.sem" please? That's the only way I know to limit semaphores and the usual limits on Linux are in the 1G range.

Here's the output

sysctl kernel.sem
kernel.sem = 32000 1024000000 500 32000

I ran the same tests on the rhel 8 system, I don't see any crashes.


Thanks
Numan
> >
> >>
> >> The usage of the function - can_parallelize_hashes() in ovn-northd.c is very
> >> confusing to me.
> >>
> >> I see that ovn_can_parallelize_hashes() calls setup_worker_pools() only once
> >> and for the subsequent calls, this function will be a no-op (due to
> >> atomic_compare_exchange_strong()).
> >>
> >> Since this function is called before the workers are started, what is
> >> the need to use
> >> atomic_compare_exchange_strong() ?
> >
> > We have ended there over time. There was a point where there was no option and no initial invocation wasn't and we were invoking the set-up on first processing.
> >
> > In fact that is how it is invoked in the OVS codebase port for the parallelized monitors. I would actually like to keep this as an option.
> >
> >>
> >> Let's say we want to add another config option -
> >> force_northd_parallel, and if the user
> >> toggles the value between the runs, then the below code in
> >> ovnnb_db_run() in patch 3
> >>
> >> ---
> >> use_parallel_build = smap_get_bool(&nb->options,
> >> "use_parallel_build", false) &&
> >> ovn_can_parallelize_hashes(false);
> >> --
> >>   will have no effect since setup_worker_pools() is not called later
> >> once the atomic
> >> bool initial_pool_setup is set to true.
> >>
> >> I think we should provide the option to toggle this value at run time.
> >> Also the patch 3 should
> >> add an option to configure the force_parallel.
> >>
> >>> ---
> >>>   lib/automake.mk         |   2 +
> >>>   lib/ovn-parallel-hmap.c | 455 ++++++++++++++++++++++++++++++++++++++++
> >>>   lib/ovn-parallel-hmap.h | 285 +++++++++++++++++++++++++
> >>>   3 files changed, 742 insertions(+)
> >>>   create mode 100644 lib/ovn-parallel-hmap.c
> >>>   create mode 100644 lib/ovn-parallel-hmap.h
> >>>
> >>> diff --git a/lib/automake.mk b/lib/automake.mk
> >>> index 250c7aefa..781be2109 100644
> >>> --- a/lib/automake.mk
> >>> +++ b/lib/automake.mk
> >>> @@ -13,6 +13,8 @@ lib_libovn_la_SOURCES = \
> >>>          lib/expr.c \
> >>>          lib/extend-table.h \
> >>>          lib/extend-table.c \
> >>> +       lib/ovn-parallel-hmap.h \
> >>> +       lib/ovn-parallel-hmap.c \
> >>>          lib/ip-mcast-index.c \
> >>>          lib/ip-mcast-index.h \
> >>>          lib/mcast-group-index.c \
> >>> diff --git a/lib/ovn-parallel-hmap.c b/lib/ovn-parallel-hmap.c
> >>> new file mode 100644
> >>> index 000000000..06aa95aba
> >>> --- /dev/null
> >>> +++ b/lib/ovn-parallel-hmap.c
> >>> @@ -0,0 +1,455 @@
> >>> +/*
> >>> + * Copyright (c) 2020 Red Hat, Inc.
> >>> + * Copyright (c) 2008, 2009, 2010, 2012, 2013, 2015, 2019 Nicira, Inc.
> >>> + *
> >>> + * Licensed under the Apache License, Version 2.0 (the "License");
> >>> + * you may not use this file except in compliance with the License.
> >>> + * You may obtain a copy of the License at:
> >>> + *
> >>> + *     http://www.apache.org/licenses/LICENSE-2.0
> >>> + *
> >>> + * Unless required by applicable law or agreed to in writing, software
> >>> + * distributed under the License is distributed on an "AS IS" BASIS,
> >>> + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
> >>> + * See the License for the specific language governing permissions and
> >>> + * limitations under the License.
> >>> + */
> >>> +
> >>> +#include <config.h>
> >>> +#include <stdint.h>
> >>> +#include <string.h>
> >>> +#include <stdlib.h>
> >>> +#include <fcntl.h>
> >>> +#include <unistd.h>
> >>> +#include <errno.h>
> >>> +#include <semaphore.h>
> >>> +#include "fatal-signal.h"
> >>> +#include "util.h"
> >>> +#include "openvswitch/vlog.h"
> >>> +#include "openvswitch/hmap.h"
> >>> +#include "openvswitch/thread.h"
> >>> +#include "ovn-parallel-hmap.h"
> >>> +#include "ovs-atomic.h"
> >>> +#include "ovs-thread.h"
> >>> +#include "ovs-numa.h"
> >>> +#include "random.h"
> >>> +
> >>> +VLOG_DEFINE_THIS_MODULE(ovn_parallel_hmap);
> >>> +
> >>> +#ifndef OVS_HAS_PARALLEL_HMAP
> >>> +
> >>> +#define WORKER_SEM_NAME "%x-%p-%x"
> >>> +#define MAIN_SEM_NAME "%x-%p-main"
> >>> +
> >>> +/* These are accessed under mutex inside add_worker_pool().
> >>> + * They do not need to be atomic.
> >>> + */
> >>> +
> >>> +static atomic_bool initial_pool_setup = ATOMIC_VAR_INIT(false);
> >>> +static bool can_parallelize = false;
> >>> +
> >>> +/* This is set only in the process of exit and the set is
> >>> + * accompanied by a fence. It does not need to be atomic or be
> >>> + * accessed under a lock.
> >>> + */
> >>> +
> >>> +static bool workers_must_exit = false;
> >>> +
> >>> +static struct ovs_list worker_pools = OVS_LIST_INITIALIZER(&worker_pools);
> >>> +
> >>> +static struct ovs_mutex init_mutex = OVS_MUTEX_INITIALIZER;
> >>> +
> >>> +static int pool_size;
> >>> +
> >>> +static int sembase;
> >>> +
> >>> +static void worker_pool_hook(void *aux OVS_UNUSED);
> >>> +static void setup_worker_pools(bool force);
> >>> +static void merge_list_results(struct worker_pool *pool OVS_UNUSED,
> >>> +                               void *fin_result, void *result_frags,
> >>> +                               int index);
> >>> +static void merge_hash_results(struct worker_pool *pool OVS_UNUSED,
> >>> +                               void *fin_result, void *result_frags,
> >>> +                               int index);
> >>> +
> >>> +bool ovn_stop_parallel_processing(void)
> >>> +{
> >>> +    return workers_must_exit;
> >>> +}
> >>> +
> >>> +bool ovn_can_parallelize_hashes(bool force_parallel)
> >>> +{
> >>> +    bool test = false;
> >>> +
> >>> +    if (atomic_compare_exchange_strong(
> >>> +            &initial_pool_setup,
> >>> +            &test,
> >>> +            true)) {
> >>> +        ovs_mutex_lock(&init_mutex);
> >>> +        setup_worker_pools(force_parallel);
> >>> +        ovs_mutex_unlock(&init_mutex);
> >>> +    }
> >>> +    return can_parallelize;
> >>> +}
> >>> +
> >>> +struct worker_pool *ovn_add_worker_pool(void *(*start)(void *)){
> >>> +
> >>> +    struct worker_pool *new_pool = NULL;
> >>> +    struct worker_control *new_control;
> >>> +    bool test = false;
> >>> +    int i;
> >>> +    char sem_name[256];
> >>> +
> >>> +
> >>> +    /* Belt and braces - initialize the pool system just in case if
> >>> +     * if it is not yet initialized.
> >>> +     */
> >>> +
> >>> +    if (atomic_compare_exchange_strong(
> >>> +            &initial_pool_setup,
> >>> +            &test,
> >>> +            true)) {
> >>> +        ovs_mutex_lock(&init_mutex);
> >>> +        setup_worker_pools(false);
> >>> +        ovs_mutex_unlock(&init_mutex);
> >>> +    }
> >>> +
> >>> +    ovs_mutex_lock(&init_mutex);
> >>> +    if (can_parallelize) {
> >>> +        new_pool = xmalloc(sizeof(struct worker_pool));
> >>> +        new_pool->size = pool_size;
> >>> +        new_pool->controls = NULL;
> >>> +        sprintf(sem_name, MAIN_SEM_NAME, sembase, new_pool);
> >>> +        new_pool->done = sem_open(sem_name, O_CREAT, S_IRWXU, 0);
> >>> +        if (new_pool->done == SEM_FAILED) {
> >>> +            goto cleanup;
> >>> +        }
> >>> +
> >>> +        new_pool->controls =
> >>> +            xmalloc(sizeof(struct worker_control) * new_pool->size);
> >>> +
> >>> +        for (i = 0; i < new_pool->size; i++) {
> >>> +            new_control = &new_pool->controls[i];
> >>> +            new_control->id = i;
> >>> +            new_control->done = new_pool->done;
> >>> +            new_control->data = NULL;
> >>> +            ovs_mutex_init(&new_control->mutex);
> >>> +            new_control->finished = ATOMIC_VAR_INIT(false);
> >>> +            sprintf(sem_name, WORKER_SEM_NAME, sembase, new_pool, i);
> >>> +            new_control->fire = sem_open(sem_name, O_CREAT, S_IRWXU, 0);
> >>> +            if (new_control->fire == SEM_FAILED) {
> >>> +                goto cleanup;
> >>> +            }
> >>> +        }
> >>> +
> >>> +        for (i = 0; i < pool_size; i++) {
> >>> +            ovs_thread_create("worker pool helper", start, &new_pool->controls[i]);
> >>> +        }
> >>> +        ovs_list_push_back(&worker_pools, &new_pool->list_node);
> >>> +    }
> >>> +    ovs_mutex_unlock(&init_mutex);
> >>> +    return new_pool;
> >>> +cleanup:
> >>> +
> >>> +    /* Something went wrong when opening semaphores. In this case
> >>> +     * it is better to shut off parallel procesing altogether
> >>> +     */
> >>> +
> >>> +    VLOG_INFO("Failed to initialize parallel processing, error %d", errno);
> >>> +    can_parallelize = false;
> >>> +    if (new_pool->controls) {
> >>> +        for (i = 0; i < new_pool->size; i++) {
> >>> +            if (new_pool->controls[i].fire != SEM_FAILED) {
> >>> +                sem_close(new_pool->controls[i].fire);
> >>> +                sprintf(sem_name, WORKER_SEM_NAME, sembase, new_pool, i);
> >>> +                sem_unlink(sem_name);
> >>> +                break; /* semaphores past this one are uninitialized */
> >>> +            }
> >>> +        }
> >>> +    }
> >>> +    if (new_pool->done != SEM_FAILED) {
> >>> +        sem_close(new_pool->done);
> >>> +        sprintf(sem_name, MAIN_SEM_NAME, sembase, new_pool);
> >>> +        sem_unlink(sem_name);
> >>> +    }
> >>> +    ovs_mutex_unlock(&init_mutex);
> >>> +    return NULL;
> >>> +}
> >>> +
> >>> +
> >>> +/* Initializes 'hmap' as an empty hash table with mask N. */
> >>> +void
> >>> +ovn_fast_hmap_init(struct hmap *hmap, ssize_t mask)
> >>> +{
> >>> +    size_t i;
> >>> +
> >>> +    hmap->buckets = xmalloc(sizeof (struct hmap_node *) * (mask + 1));
> >>> +    hmap->one = NULL;
> >>> +    hmap->mask = mask;
> >>> +    hmap->n = 0;
> >>> +    for (i = 0; i <= hmap->mask; i++) {
> >>> +        hmap->buckets[i] = NULL;
> >>> +    }
> >>> +}
> >>> +
> >>> +/* Initializes 'hmap' as an empty hash table of size X.
> >>> + * Intended for use in parallel processing so that all
> >>> + * fragments used to store results in a parallel job
> >>> + * are the same size.
> >>> + */
> >>> +void
> >>> +ovn_fast_hmap_size_for(struct hmap *hmap, int size)
> >>> +{
> >>> +    size_t mask;
> >>> +    mask = size / 2;
> >>> +    mask |= mask >> 1;
> >>> +    mask |= mask >> 2;
> >>> +    mask |= mask >> 4;
> >>> +    mask |= mask >> 8;
> >>> +    mask |= mask >> 16;
> >>> +#if SIZE_MAX > UINT32_MAX
> >>> +    mask |= mask >> 32;
> >>> +#endif
> >>> +
> >>> +    /* If we need to dynamically allocate buckets we might as well allocate at
> >>> +     * least 4 of them. */
> >>> +    mask |= (mask & 1) << 1;
> >>> +
> >>> +    fast_hmap_init(hmap, mask);
> >>> +}
> >>> +
> >>> +/* Run a thread pool which uses a callback function to process results
> >>> + */
> >>> +
> >>> +void ovn_run_pool_callback(struct worker_pool *pool,
> >>> +                           void *fin_result, void *result_frags,
> >>> +                           void (*helper_func)(struct worker_pool *pool,
> >>> +                                               void *fin_result,
> >>> +                                               void *result_frags, int index))
> >>> +{
> >>> +    int index, completed;
> >>> +
> >>> +    /* Ensure that all worker threads see the same data as the
> >>> +     * main thread.
> >>> +     */
> >>> +
> >>> +    atomic_thread_fence(memory_order_acq_rel);
> >>> +
> >>> +    /* Start workers */
> >>> +
> >>> +    for (index = 0; index < pool->size; index++) {
> >>> +        sem_post(pool->controls[index].fire);
> >>> +    }
> >>> +
> >>> +    completed = 0;
> >>> +
> >>> +    do {
> >>> +        bool test;
> >>> +        /* Note - we do not loop on semaphore until it reaches
> >>> +         * zero, but on pool size/remaining workers.
> >>> +         * This is by design. If the inner loop can handle
> >>> +         * completion for more than one worker within an iteration
> >>> +         * it will do so to ensure no additional iterations and
> >>> +         * waits once all of them are done.
> >>> +         *
> >>> +         * This may result in us having an initial positive value
> >>> +         * of the semaphore when the pool is invoked the next time.
> >>> +         * This is harmless - the loop will spin up a couple of times
> >>> +         * doing nothing while the workers are processing their data
> >>> +         * slices.
> >>> +         */
> >>> +        sem_wait(pool->done);
> >>> +        for (index = 0; index < pool->size; index++) {
> >>> +            test = true;
> >>> +            /* If the worker has marked its data chunk as complete,
> >>> +             * invoke the helper function to combine the results of
> >>> +             * this worker into the main result.
> >>> +             *
> >>> +             * The worker must invoke an appropriate memory fence
> >>> +             * (most likely acq_rel) to ensure that the main thread
> >>> +             * sees all of the results produced by the worker.
> >>> +             */
> >>> +            if (atomic_compare_exchange_weak(
> >>> +                    &pool->controls[index].finished,
> >>> +                    &test,
> >>> +                    false)) {
> >>> +                if (helper_func) {
> >>> +                    (helper_func)(pool, fin_result, result_frags, index);
> >>> +                }
> >>> +                completed++;
> >>> +                pool->controls[index].data = NULL;
> >>> +            }
> >>> +        }
> >>> +    } while (completed < pool->size);
> >>> +}
> >>> +
> >>> +/* Run a thread pool - basic, does not do results processing.
> >>> + */
> >>> +
> >>> +void ovn_run_pool(struct worker_pool *pool)
> >>> +{
> >>> +    run_pool_callback(pool, NULL, NULL, NULL);
> >>> +}
> >>> +
> >>> +/* Brute force merge of a hashmap into another hashmap.
> >>> + * Intended for use in parallel processing. The destination
> >>> + * hashmap MUST be the same size as the one being merged.
> >>> + *
> >>> + * This can be achieved by pre-allocating them to correct size
> >>> + * and using hmap_insert_fast() instead of hmap_insert()
> >>> + */
> >>> +
> >>> +void ovn_fast_hmap_merge(struct hmap *dest, struct hmap *inc)
> >>> +{
> >>> +    size_t i;
> >>> +
> >>> +    ovs_assert(inc->mask == dest->mask);
> >>> +
> >>> +    if (!inc->n) {
> >>> +        /* Request to merge an empty frag, nothing to do */
> >>> +        return;
> >>> +    }
> >>> +
> >>> +    for (i = 0; i <= dest->mask; i++) {
> >>> +        struct hmap_node **dest_bucket = &dest->buckets[i];
> >>> +        struct hmap_node **inc_bucket = &inc->buckets[i];
> >>> +        if (*inc_bucket != NULL) {
> >>> +            struct hmap_node *last_node = *inc_bucket;
> >>> +            while (last_node->next != NULL) {
> >>> +                last_node = last_node->next;
> >>> +            }
> >>> +            last_node->next = *dest_bucket;
> >>> +            *dest_bucket = *inc_bucket;
> >>> +            *inc_bucket = NULL;
> >>> +        }
> >>> +    }
> >>> +    dest->n += inc->n;
> >>> +    inc->n = 0;
> >>> +}
> >>> +
> >>> +/* Run a thread pool which gathers results in an array
> >>> + * of hashes. Merge results.
> >>> + */
> >>> +
> >>> +
> >>> +void ovn_run_pool_hash(
> >>> +        struct worker_pool *pool,
> >>> +        struct hmap *result,
> >>> +        struct hmap *result_frags)
> >>> +{
> >>> +    run_pool_callback(pool, result, result_frags, merge_hash_results);
> >>> +}
> >>> +
> >>> +/* Run a thread pool which gathers results in an array of lists.
> >>> + * Merge results.
> >>> + */
> >>> +void ovn_run_pool_list(
> >>> +        struct worker_pool *pool,
> >>> +        struct ovs_list *result,
> >>> +        struct ovs_list *result_frags)
> >>> +{
> >>> +    run_pool_callback(pool, result, result_frags, merge_list_results);
> >>> +}
> >>> +
> >>> +void ovn_update_hashrow_locks(struct hmap *lflows, struct hashrow_locks *hrl)
> >>> +{
> >>> +    int i;
> >>> +    if (hrl->mask != lflows->mask) {
> >>> +        if (hrl->row_locks) {
> >>> +            free(hrl->row_locks);
> >>> +        }
> >>> +        hrl->row_locks = xcalloc(sizeof(struct ovs_mutex), lflows->mask + 1);
> >>> +        hrl->mask = lflows->mask;
> >>> +        for (i = 0; i <= lflows->mask; i++) {
> >>> +            ovs_mutex_init(&hrl->row_locks[i]);
> >>> +        }
> >>> +    }
> >>> +}
> >>> +
> >>> +static void worker_pool_hook(void *aux OVS_UNUSED) {
> >>> +    int i;
> >>> +    static struct worker_pool *pool;
> >>> +    char sem_name[256];
> >>> +
> >>> +    workers_must_exit = true;
> >>> +
> >>> +    /* All workers must honour the must_exit flag and check for it regularly.
> >>> +     * We can make it atomic and check it via atomics in workers, but that
> >>> +     * is not really necessary as it is set just once - when the program
> >>> +     * terminates. So we use a fence which is invoked before exiting instead.
> >>> +     */
> >>> +    atomic_thread_fence(memory_order_acq_rel);
> >>> +
> >>> +    /* Wake up the workers after the must_exit flag has been set */
> >>> +
> >>> +    LIST_FOR_EACH (pool, list_node, &worker_pools) {
> >>> +        for (i = 0; i < pool->size ; i++) {
> >>> +            sem_post(pool->controls[i].fire);
> >>> +        }
> >>> +        for (i = 0; i < pool->size ; i++) {
> >>> +            sem_close(pool->controls[i].fire);
> >>> +            sprintf(sem_name, WORKER_SEM_NAME, sembase, pool, i);
> >>> +            sem_unlink(sem_name);
> >>> +        }
> >>> +        sem_close(pool->done);
> >>> +        sprintf(sem_name, MAIN_SEM_NAME, sembase, pool);
> >>> +        sem_unlink(sem_name);
> >>> +    }
> >>> +}
> >>> +
> >>> +static void setup_worker_pools(bool force) {
> >>> +    int cores, nodes;
> >>> +
> >>> +    nodes = ovs_numa_get_n_numas();
> >>> +    if (nodes == OVS_NUMA_UNSPEC || nodes <= 0) {
> >>> +        nodes = 1;
> >>> +    }
> >>> +    cores = ovs_numa_get_n_cores();
> >>> +
> >>> +    /* If there is no NUMA config, use 4 cores.
> >>> +     * If there is NUMA config use half the cores on
> >>> +     * one node so that the OS does not start pushing
> >>> +     * threads to other nodes.
> >>> +     */
> >>> +    if (cores == OVS_CORE_UNSPEC || cores <= 0) {
> >>> +        /* If there is no NUMA we can try the ovs-threads routine.
> >>> +         * It falls back to sysconf and/or affinity mask.
> >>> +         */
> >>> +        cores = count_cpu_cores();
> >>> +        pool_size = cores;
> >>> +    } else {
> >>> +        pool_size = cores / nodes;
> >>> +    }
> >>> +    if ((pool_size < 4) && force) {
> >>> +        pool_size = 4;
> >>> +    }
> >>> +    can_parallelize = (pool_size >= 3);
> >>> +    fatal_signal_add_hook(worker_pool_hook, NULL, NULL, true);
> >>> +    sembase = random_uint32();
> >>> +}
> >>> +
> >>> +static void merge_list_results(struct worker_pool *pool OVS_UNUSED,
> >>> +                               void *fin_result, void *result_frags,
> >>> +                               int index)
> >>> +{
> >>> +    struct ovs_list *result = (struct ovs_list *)fin_result;
> >>> +    struct ovs_list *res_frags = (struct ovs_list *)result_frags;
> >>> +
> >>> +    if (!ovs_list_is_empty(&res_frags[index])) {
> >>> +        ovs_list_splice(result->next,
> >>> +                ovs_list_front(&res_frags[index]), &res_frags[index]);
> >>> +    }
> >>> +}
> >>> +
> >>> +static void merge_hash_results(struct worker_pool *pool OVS_UNUSED,
> >>> +                               void *fin_result, void *result_frags,
> >>> +                               int index)
> >>> +{
> >>> +    struct hmap *result = (struct hmap *)fin_result;
> >>> +    struct hmap *res_frags = (struct hmap *)result_frags;
> >>> +
> >>> +    fast_hmap_merge(result, &res_frags[index]);
> >>> +    hmap_destroy(&res_frags[index]);
> >>> +}
> >>> +
> >>> +#endif
> >>> diff --git a/lib/ovn-parallel-hmap.h b/lib/ovn-parallel-hmap.h
> >>> new file mode 100644
> >>> index 000000000..71ad17fb0
> >>> --- /dev/null
> >>> +++ b/lib/ovn-parallel-hmap.h
> >>> @@ -0,0 +1,285 @@
> >>> +/*
> >>> + * Copyright (c) 2020 Red Hat, Inc.
> >>> + *
> >>> + * Licensed under the Apache License, Version 2.0 (the "License");
> >>> + * you may not use this file except in compliance with the License.
> >>> + * You may obtain a copy of the License at:
> >>> + *
> >>> + *     http://www.apache.org/licenses/LICENSE-2.0
> >>> + *
> >>> + * Unless required by applicable law or agreed to in writing, software
> >>> + * distributed under the License is distributed on an "AS IS" BASIS,
> >>> + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
> >>> + * See the License for the specific language governing permissions and
> >>> + * limitations under the License.
> >>> + */
> >>> +
> >>> +#ifndef OVN_PARALLEL_HMAP
> >>> +#define OVN_PARALLEL_HMAP 1
> >>> +
> >>> +/* if the parallel macros are defined by hmap.h or any other ovs define
> >>> + * we skip over the ovn specific definitions.
> >>> + */
> >>> +
> >>> +#ifdef  __cplusplus
> >>> +extern "C" {
> >>> +#endif
> >>> +
> >>> +#include <stdbool.h>
> >>> +#include <stdlib.h>
> >>> +#include <semaphore.h>
> >>> +#include "openvswitch/util.h"
> >>> +#include "openvswitch/hmap.h"
> >>> +#include "openvswitch/thread.h"
> >>> +#include "ovs-atomic.h"
> >>> +
> >>> +/* Process this include only if OVS does not supply parallel definitions
> >>> + */
> >>> +
> >>> +#ifdef OVS_HAS_PARALLEL_HMAP
> >>> +
> >>> +#include "parallel-hmap.h"
> >>> +
> >>> +#else
> >>> +
> >>> +
> >>> +#ifdef __clang__
> >>> +#pragma clang diagnostic push
> >>> +#pragma clang diagnostic ignored "-Wthread-safety"
> >>> +#endif
> >> I think you missed addressing my comment I provided in v13 to
> >> add some comments on why this is required.
> >>
> >>
> >>> +
> >>> +
> >>> +/* A version of the HMAP_FOR_EACH macro intended for iterating as part
> >>> + * of parallel processing.
> >>> + * Each worker thread has a different ThreadID in the range of 0..POOL_SIZE
> >>> + * and will iterate hash buckets ThreadID, ThreadID + step,
> >>> + * ThreadID + step * 2, etc. The actual macro accepts
> >>> + * ThreadID + step * i as the JOBID parameter.
> >>> + */
> >>> +
> >>> +#define HMAP_FOR_EACH_IN_PARALLEL(NODE, MEMBER, JOBID, HMAP) \
> >>> +   for (INIT_CONTAINER(NODE, hmap_first_in_bucket_num(HMAP, JOBID), MEMBER); \
> >>> +        (NODE != OBJECT_CONTAINING(NULL, NODE, MEMBER)) \
> >>> +       || ((NODE = NULL), false); \
> >>> +       ASSIGN_CONTAINER(NODE, hmap_next_in_bucket(&(NODE)->MEMBER), MEMBER))
> >>> +
> >>> +/* We do not have a SAFE version of the macro, because the hash size is not
> >>> + * atomic and hash removal operations would need to be wrapped with
> >>> + * locks. This will defeat most of the benefits from doing anything in
> >>> + * parallel.
> >>> + * If the code block inside FOR_EACH_IN_PARALLEL needs to remove elements,
> >>> + * each thread should store them in a temporary list result instead, merging
> >>> + * the lists into a combined result at the end */
> >>> +
> >>> +/* Work "Handle" */
> >>> +
> >>> +struct worker_control {
> >>> +    int id; /* Used as a modulo when iterating over a hash. */
> >>> +    atomic_bool finished; /* Set to true after achunk of work is complete. */
> >>> +    sem_t *fire; /* Work start semaphore - sem_post starts the worker. */
> >>> +    sem_t *done; /* Work completion semaphore - sem_post on completion. */
> >>> +    struct ovs_mutex mutex; /* Guards the data. */
> >>> +    void *data; /* Pointer to data to be processed. */
> >>> +    void *workload; /* back-pointer to the worker pool structure. */
> >>> +};
> >>> +
> >>> +struct worker_pool {
> >>> +    int size;   /* Number of threads in the pool. */
> >>> +    struct ovs_list list_node; /* List of pools - used in cleanup/exit. */
> >>> +    struct worker_control *controls; /* "Handles" in this pool. */
> >>> +    sem_t *done; /* Work completion semaphorew. */
> >>> +};
> >>> +
> >>> +/* Add a worker pool for thread function start() which expects a pointer to
> >>> + * a worker_control structure as an argument. */
> >>> +
> >>> +struct worker_pool *ovn_add_worker_pool(void *(*start)(void *));
> >>> +
> >>> +/* Setting this to true will make all processing threads exit */
> >>> +
> >>> +bool ovn_stop_parallel_processing(void);
> >>> +
> >>> +/* Build a hmap pre-sized for size elements */
> >>> +
> >>> +void ovn_fast_hmap_size_for(struct hmap *hmap, int size);
> >>> +
> >>> +/* Build a hmap with a mask equals to size */
> >>> +
> >>> +void ovn_fast_hmap_init(struct hmap *hmap, ssize_t size);
> >>> +
> >>> +/* Brute-force merge a hmap into hmap.
> >>> + * Dest and inc have to have the same mask. The merge is performed
> >>> + * by extending the element list for bucket N in the dest hmap with the list
> >>> + * from bucket N in inc.
> >>> + */
> >>> +
> >>> +void ovn_fast_hmap_merge(struct hmap *dest, struct hmap *inc);
> >>> +
> >>> +/* Run a pool, without any default processing of results.
> >>> + */
> >>> +
> >>> +void ovn_run_pool(struct worker_pool *pool);
> >>> +
> >>> +/* Run a pool, merge results from hash frags into a final hash result.
> >>> + * The hash frags must be pre-sized to the same size.
> >>> + */
> >>> +
> >>> +void ovn_run_pool_hash(struct worker_pool *pool,
> >>> +                       struct hmap *result, struct hmap *result_frags);
> >>> +/* Run a pool, merge results from list frags into a final list result.
> >>> + */
> >>> +
> >>> +void ovn_run_pool_list(struct worker_pool *pool,
> >>> +                       struct ovs_list *result, struct ovs_list *result_frags);
> >>> +
> >>> +/* Run a pool, call a callback function to perform processing of results.
> >>> + */
> >>> +
> >>> +void ovn_run_pool_callback(struct worker_pool *pool, void *fin_result,
> >>> +                    void *result_frags,
> >>> +                    void (*helper_func)(struct worker_pool *pool,
> >>> +                        void *fin_result, void *result_frags, int index));
> >>> +
> >>> +
> >>> +/* Returns the first node in 'hmap' in the bucket in which the given 'hash'
> >>> + * would land, or a null pointer if that bucket is empty. */
> >>> +
> >>> +static inline struct hmap_node *
> >>> +hmap_first_in_bucket_num(const struct hmap *hmap, size_t num)
> >>> +{
> >>> +    return hmap->buckets[num];
> >>> +}
> >>> +
> >>> +static inline struct hmap_node *
> >>> +parallel_hmap_next__(const struct hmap *hmap, size_t start, size_t pool_size)
> >>> +{
> >>> +    size_t i;
> >>> +    for (i = start; i <= hmap->mask; i+= pool_size) {
> >>> +        struct hmap_node *node = hmap->buckets[i];
> >>> +        if (node) {
> >>> +            return node;
> >>> +        }
> >>> +    }
> >>> +    return NULL;
> >>> +}
> >>> +
> >>> +/* Returns the first node in 'hmap', as expected by thread with job_id
> >>> + * for parallel processing in arbitrary order, or a null pointer if
> >>> + * the slice of 'hmap' for that job_id is empty. */
> >>> +static inline struct hmap_node *
> >>> +parallel_hmap_first(const struct hmap *hmap, size_t job_id, size_t pool_size)
> >>> +{
> >>> +    return parallel_hmap_next__(hmap, job_id, pool_size);
> >>> +}
> >>> +
> >>> +/* Returns the next node in the slice of 'hmap' following 'node',
> >>> + * in arbitrary order, or a * null pointer if 'node' is the last node in
> >>> + * the 'hmap' slice.
> >>> + *
> >>> + */
> >>> +static inline struct hmap_node *
> >>> +parallel_hmap_next(const struct hmap *hmap,
> >>> +                   const struct hmap_node *node, ssize_t pool_size)
> >>> +{
> >>> +    return (node->next
> >>> +            ? node->next
> >>> +            : parallel_hmap_next__(hmap,
> >>> +                (node->hash & hmap->mask) + pool_size, pool_size));
> >>> +}
> >>> +
> >>> +static inline void post_completed_work(struct worker_control *control)
> >>> +{
> >>> +    atomic_thread_fence(memory_order_acq_rel);
> >>> +    atomic_store_relaxed(&control->finished, true);
> >>> +    sem_post(control->done);
> >>> +}
> >>> +
> >>> +static inline void wait_for_work(struct worker_control *control)
> >>> +{
> >>> +    sem_wait(control->fire);
> >>> +}
> >>> +
> >>> +/* Hash per-row locking support - to be used only in conjunction
> >>> + * with fast hash inserts. Normal hash inserts may resize the hash
> >>> + * rendering the locking invalid.
> >>> + */
> >>> +
> >>> +struct hashrow_locks {
> >>> +    ssize_t mask;
> >>> +    struct ovs_mutex *row_locks;
> >>> +};
> >>> +
> >>> +/* Update an hash row locks structure to match the current hash size */
> >>> +
> >>> +void ovn_update_hashrow_locks(struct hmap *lflows, struct hashrow_locks *hrl);
> >>> +
> >>> +/* Lock a hash row */
> >>> +
> >>> +static inline void lock_hash_row(struct hashrow_locks *hrl, uint32_t hash)
> >>> +{
> >>> +    ovs_mutex_lock(&hrl->row_locks[hash % hrl->mask]);
> >>> +}
> >>> +
> >>> +/* Unlock a hash row */
> >>> +
> >>> +static inline void unlock_hash_row(struct hashrow_locks *hrl, uint32_t hash)
> >>> +{
> >>> +    ovs_mutex_unlock(&hrl->row_locks[hash % hrl->mask]);
> >>> +}
> >>> +/* Init the row locks structure */
> >>> +
> >>> +static inline void init_hash_row_locks(struct hashrow_locks *hrl)
> >>> +{
> >>> +    hrl->mask = 0;
> >>> +    hrl->row_locks = NULL;
> >>> +}
> >>> +
> >>> +bool ovn_can_parallelize_hashes(bool force_parallel);
> >>> +
> >>> +/* Use the OVN library functions for stuff which OVS has not defined
> >>> + * If OVS has defined these, they will still compile using the OVN
> >>> + * local names, but will be dropped by the linker in favour of the OVS
> >>> + * supplied functions.
> >>> + */
> >>> +
> >>> +#define update_hashrow_locks(lflows, hrl) ovn_update_hashrow_locks(lflows, hrl)
> >>> +
> >>> +#define can_parallelize_hashes(force) ovn_can_parallelize_hashes(force)
> >>> +
> >>> +#define stop_parallel_processing() ovn_stop_parallel_processing()
> >>> +
> >>> +#define add_worker_pool(start) ovn_add_worker_pool(start)
> >>> +
> >>> +#define fast_hmap_size_for(hmap, size) ovn_fast_hmap_size_for(hmap, size)
> >>> +
> >>> +#define fast_hmap_init(hmap, size) ovn_fast_hmap_init(hmap, size)
> >>> +
> >>> +#define fast_hmap_merge(dest, inc) ovn_fast_hmap_merge(dest, inc)
> >>> +
> >>> +#define hmap_merge(dest, inc) ovn_hmap_merge(dest, inc)
> >>> +
> >>> +#define ovn_run_pool(pool) ovn_run_pool(pool)
> >>> +
> >>> +#define run_pool_hash(pool, result, result_frags) \
> >>> +    ovn_run_pool_hash(pool, result, result_frags)
> >>> +
> >>> +#define run_pool_list(pool, result, result_frags) \
> >>> +    ovn_run_pool_list(pool, result, result_frags)
> >>> +
> >>> +#define run_pool_callback(pool, fin_result, result_frags, helper_func) \
> >>> +    ovn_run_pool_callback(pool, fin_result, result_frags, helper_func)
> >>> +
> >>> +
> >> In my opinion, we can switch over to making use of OVS APIs for fast_hmap
> >> once the patches in OVS are merged.  Until then I think we should just assume
> >> that these functions are part of OVN lib and consume them directly.
> >>
> >> It's possible that the function names could change when those patches
> >> land in OVS.
> >>
> >> Thanks
> >> Numan
> >>
> >>> +
> >>> +#ifdef __clang__
> >>> +#pragma clang diagnostic pop
> >>> +#endif
> >>> +
> >>> +#endif
> >>> +
> >>> +#ifdef  __cplusplus
> >>> +}
> >>> +#endif
> >>> +
> >>> +
> >>> +#endif /* lib/fasthmap.h */
> >>> --
> >>> 2.20.1
> >>>
> >>> _______________________________________________
> >>> dev mailing list
> >>> dev at openvswitch.org
> >>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >>>
>
> --
> Anton R. Ivanov
> Cambridgegreys Limited. Registered in England. Company Number 10273661
> https://www.cambridgegreys.com/
>
> _______________________________________________
> dev mailing list
> dev at openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-dev



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