[ovs-dev] [OVN Patch v15 1/3] ovn-libs: Add support for parallel processing

Anton Ivanov anton.ivanov at cambridgegreys.com
Thu Mar 25 09:30:51 UTC 2021



On 24/03/2021 15:31, Numan Siddique wrote:
> On Mon, Mar 1, 2021 at 6:35 PM <anton.ivanov at cambridgegreys.com> wrote:
>>
>> From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
>>
>> This adds a set of functions and macros intended to process
>> hashes in parallel.
>>
>> The principles of operation are documented in the ovn-parallel-hmap.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 tested the first 2 patches of this series and it crashes again for me.
> 
> This time I ran tests on a 4 core  machine - Intel(R) Xeon(R) CPU
> E3-1220 v5 @ 3.00GHz
> 
> The below trace is seen for both gcc and clang.
> 
> ----
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib64/libthread_db.so.1".
> Core was generated by `ovn-northd -vjsonrpc
> --ovnnb-db=unix:/mnt/mydisk/myhome/numan_alt/work/ovs_ovn/'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  0x00007f27594ae212 in __new_sem_wait_slow.constprop.0 () from
> /lib64/libpthread.so.0
> [Current thread is 1 (Thread 0x7f2758c68640 (LWP 347378))]
> 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  0x00007f27594ae212 in __new_sem_wait_slow.constprop.0 () from
> /lib64/libpthread.so.0
> #1  0x0000000000422184 in wait_for_work (control=<optimized out>) at
> ../lib/ovn-parallel-hmap.h:203
> #2  build_lflows_thread (arg=0x2538420) at ../northd/ovn-northd.c:11855
> #3  0x000000000049cd12 in ovsthread_wrapper (aux_=<optimized out>) at
> ../lib/ovs-thread.c:383
> #4  0x00007f27594a53f9 in start_thread () from /lib64/libpthread.so.0
> #5  0x00007f2759142903 in clone () from /lib64/libc.so.6
> -----
> 
> I'm not sure why you're not able to reproduce this issue.

I can't. I have run it for days in a loop.

One possibility is that for whatever reason your machine has slower IPC speeds compared to linear execution speeds. Thread debugging? AMD vs Intel? No idea.

There is a race on-exit in the current code which I have found by inspection and which I have never been able to trigger. On my machines the workers always exit in time before the main thread has finished, so I cannot trigger this.

Can you try this incremental fix to see if it fixes the problem for you. If that works, I will incorporate it and reissue the patch. If not - I will continue digging.

diff --git a/lib/ovn-parallel-hmap.c b/lib/ovn-parallel-hmap.c
index e83ae23cb..3597f896f 100644
--- a/lib/ovn-parallel-hmap.c
+++ b/lib/ovn-parallel-hmap.c
@@ -143,7 +143,8 @@ struct worker_pool *ovn_add_worker_pool(void *(*start)(void *)){
          }

          for (i = 0; i < pool_size; i++) {
-            ovs_thread_create("worker pool helper", start, &new_pool->controls[i]);
+            new_pool->controls[i].worker =
+                ovs_thread_create("worker pool helper", start, &new_pool->controls[i]);
          }
          ovs_list_push_back(&worker_pools, &new_pool->list_node);
      }
@@ -386,6 +387,9 @@ static void worker_pool_hook(void *aux OVS_UNUSED) {
          for (i = 0; i < pool->size ; i++) {
              sem_post(pool->controls[i].fire);
          }
+        for (i = 0; i < pool->size ; i++) {
+            pthread_join(pool->controls[i].worker, NULL);
+        }
          for (i = 0; i < pool->size ; i++) {
              sem_close(pool->controls[i].fire);
              sprintf(sem_name, WORKER_SEM_NAME, sembase, pool, i);
diff --git a/lib/ovn-parallel-hmap.h b/lib/ovn-parallel-hmap.h
index 8db61eaba..d62ca3da5 100644
--- a/lib/ovn-parallel-hmap.h
+++ b/lib/ovn-parallel-hmap.h
@@ -82,6 +82,7 @@ struct worker_control {
      struct ovs_mutex mutex; /* Guards the data. */
      void *data; /* Pointer to data to be processed. */
      void *workload; /* back-pointer to the worker pool structure. */
+    pthread_t worker;
  };

  struct worker_pool {


> 
> All the test cases passed for me. So maybe something's wrong when
> ovn-northd exits.
> IMHO, these crashes should be addressed before these patches can be considered.
> 
> Thanks
> Numan
> 
>> ---
>>   lib/automake.mk         |   2 +
>>   lib/ovn-parallel-hmap.c | 455 ++++++++++++++++++++++++++++++++++++++++
>>   lib/ovn-parallel-hmap.h | 301 ++++++++++++++++++++++++++
>>   3 files changed, 758 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..e83ae23cb
>> --- /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.
>> +         */
>> +        wait_for_work_completion(pool);
>> +        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..8db61eaba
>> --- /dev/null
>> +++ b/lib/ovn-parallel-hmap.h
>> @@ -0,0 +1,301 @@
>> +/*
>> + * 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 <errno.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
>> +
>> +
>> +/* 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)
>> +{
>> +    int ret;
>> +
>> +    do {
>> +        ret = sem_wait(control->fire);
>> +    } while ((ret == -1) && (errno == EINTR));
>> +    ovs_assert(ret == 0);
>> +}
>> +static inline void wait_for_work_completion(struct worker_pool *pool)
>> +{
>> +    int ret;
>> +
>> +    do {
>> +        ret = sem_wait(pool->done);
>> +    } while ((ret == -1) && (errno == EINTR));
>> +    ovs_assert(ret == 0);
>> +}
>> +
>> +
>> +/* 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)
>> +
>> +
>> +
>> +#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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