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

Anton Ivanov anton.ivanov at cambridgegreys.com
Thu Feb 25 14:03:01 UTC 2021


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.

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.
> 
>>
>> 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/



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