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Szmigiero" Cc: Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , =?utf-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org, Peter Xu Subject: Re: [PATCH v3 04/24] thread-pool: Implement generic (non-AIO) pool support In-Reply-To: <7efee58f-90be-44a5-92b0-7b792e1ab906@maciej.szmigiero.name> References: <87ldx7nlsj.fsf@suse.de> <7efee58f-90be-44a5-92b0-7b792e1ab906@maciej.szmigiero.name> Date: Mon, 25 Nov 2024 17:51:42 -0300 Message-ID: <87a5dnnijl.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.998]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[10]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid] Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org "Maciej S. Szmigiero" writes: > On 25.11.2024 20:41, Fabiano Rosas wrote: >> "Maciej S. Szmigiero" writes: >> >>> From: "Maciej S. Szmigiero" >>> >>> Migration code wants to manage device data sending threads in one place. >>> >>> QEMU has an existing thread pool implementation, however it is limited >>> to queuing AIO operations only and essentially has a 1:1 mapping between >>> the current AioContext and the AIO ThreadPool in use. >>> >>> Implement generic (non-AIO) ThreadPool by essentially wrapping Glib's >>> GThreadPool. >>> >>> This brings a few new operations on a pool: >>> * thread_pool_wait() operation waits until all the submitted work requests >>> have finished. >>> >>> * thread_pool_set_max_threads() explicitly sets the maximum thread count >>> in the pool. >>> >>> * thread_pool_adjust_max_threads_to_work() adjusts the maximum thread count >>> in the pool to equal the number of still waiting in queue or unfinished work. >>> >>> Signed-off-by: Maciej S. Szmigiero >>> --- >>> include/block/thread-pool.h | 9 +++ >>> util/thread-pool.c | 109 ++++++++++++++++++++++++++++++++++++ >>> 2 files changed, 118 insertions(+) >>> >>> diff --git a/include/block/thread-pool.h b/include/block/thread-pool.h >>> index 6f27eb085b45..3f9f66307b65 100644 >>> --- a/include/block/thread-pool.h >>> +++ b/include/block/thread-pool.h >>> @@ -38,5 +38,14 @@ BlockAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg, >>> int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg); >>> void thread_pool_update_params(ThreadPoolAio *pool, struct AioContext *ctx); >>> >>> +typedef struct ThreadPool ThreadPool; >>> + >>> +ThreadPool *thread_pool_new(void); >>> +void thread_pool_free(ThreadPool *pool); >>> +void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, >>> + void *opaque, GDestroyNotify opaque_destroy); >>> +void thread_pool_wait(ThreadPool *pool); >>> +bool thread_pool_set_max_threads(ThreadPool *pool, int max_threads); >>> +bool thread_pool_adjust_max_threads_to_work(ThreadPool *pool); >>> >>> #endif >>> diff --git a/util/thread-pool.c b/util/thread-pool.c >>> index 908194dc070f..d80c4181c897 100644 >>> --- a/util/thread-pool.c >>> +++ b/util/thread-pool.c >>> @@ -374,3 +374,112 @@ void thread_pool_free_aio(ThreadPoolAio *pool) >>> qemu_mutex_destroy(&pool->lock); >>> g_free(pool); >>> } >>> + >>> +struct ThreadPool { /* type safety */ >>> + GThreadPool *t; >>> + size_t unfinished_el_ctr; >>> + QemuMutex unfinished_el_ctr_mutex; >>> + QemuCond unfinished_el_ctr_zero_cond; >>> +}; >>> + >>> +typedef struct { >>> + ThreadPoolFunc *func; >>> + void *opaque; >>> + GDestroyNotify opaque_destroy; >>> +} ThreadPoolElement; >>> + >>> +static void thread_pool_func(gpointer data, gpointer user_data) >>> +{ >>> + ThreadPool *pool = user_data; >>> + g_autofree ThreadPoolElement *el = data; >>> + >>> + el->func(el->opaque); >>> + >>> + if (el->opaque_destroy) { >>> + el->opaque_destroy(el->opaque); >>> + } >>> + >>> + QEMU_LOCK_GUARD(&pool->unfinished_el_ctr_mutex); >>> + >>> + assert(pool->unfinished_el_ctr > 0); >>> + pool->unfinished_el_ctr--; >>> + >>> + if (pool->unfinished_el_ctr == 0) { >>> + qemu_cond_signal(&pool->unfinished_el_ctr_zero_cond); >>> + } >>> +} >>> + >>> +ThreadPool *thread_pool_new(void) >>> +{ >>> + ThreadPool *pool = g_new(ThreadPool, 1); >>> + >>> + pool->unfinished_el_ctr = 0; >>> + qemu_mutex_init(&pool->unfinished_el_ctr_mutex); >>> + qemu_cond_init(&pool->unfinished_el_ctr_zero_cond); >>> + >>> + pool->t = g_thread_pool_new(thread_pool_func, pool, 0, TRUE, NULL); >>> + /* >>> + * g_thread_pool_new() can only return errors if initial thread(s) >>> + * creation fails but we ask for 0 initial threads above. >>> + */ >>> + assert(pool->t); >>> + >>> + return pool; >>> +} >>> + >>> +void thread_pool_free(ThreadPool *pool) >>> +{ >>> + g_thread_pool_free(pool->t, FALSE, TRUE); >> >> Should we make it an error to call thread_poll_free without first >> calling thread_poll_wait? I worry the current usage will lead to having >> two different ways of waiting with one of them (this one) being quite >> implicit. >> > > thread_pool_wait() can be used as a barrier between two sets of > tasks executed on a thread pool without destroying it or in a performance > sensitive path where we want to just wait for task completion while > deferring the free operation for later, less sensitive time. > > I don't think requiring explicit thread_pool_wait() before > thread_pool_free() actually gives any advantage, while at the same > time it's making this API usage slightly more complex in cases > where the consumer is fine with having combined wait+free semantics > for thread_pool_free(). Fair enough, Reviewed-by: Fabiano Rosas