From patchwork Wed Jul 21 09:42:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Garzarella X-Patchwork-Id: 12390469 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2684DC07E9B for ; Wed, 21 Jul 2021 09:47:05 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C176460E0C for ; Wed, 21 Jul 2021 09:47:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C176460E0C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40830 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m68oh-0003CP-Tf for qemu-devel@archiver.kernel.org; Wed, 21 Jul 2021 05:47:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43948) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m68kH-0005HL-NH for qemu-devel@nongnu.org; Wed, 21 Jul 2021 05:42:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40425) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m68kE-0003DC-UW for qemu-devel@nongnu.org; Wed, 21 Jul 2021 05:42:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626860546; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=e6+ZiMdDFv8oHA3dnDQn58wlQWvHhmXKtz6vfzKsitY=; b=WMpnnXMhhTf7Js085m++TgP6jpgn45YmoWPHhuLHfyCamkJ3rJgoXrDSNmVdGtwtzhvm8q Ixwbtp/iXDMMPIgks4MMrQoEN8YPoIY6QBZI0nYq51VXbBwr22kTDe6UDtlNQVvCQpIiVu B1Q0jMlVQiADKIwx62GhG8SfWHMhfSU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-329-qMzj_xdJNe2rPV87SjZqkw-1; Wed, 21 Jul 2021 05:42:23 -0400 X-MC-Unique: qMzj_xdJNe2rPV87SjZqkw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 152EB107ACF5; Wed, 21 Jul 2021 09:42:22 +0000 (UTC) Received: from steredhat.redhat.com (ovpn-113-80.ams2.redhat.com [10.36.113.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6B9C760FB8; Wed, 21 Jul 2021 09:42:19 +0000 (UTC) From: Stefano Garzarella To: Stefan Hajnoczi , qemu-devel@nongnu.org Subject: [PATCH for-6.1? v2 1/3] iothread: generalize iothread_set_param/iothread_get_param Date: Wed, 21 Jul 2021 11:42:09 +0200 Message-Id: <20210721094211.69853-2-sgarzare@redhat.com> In-Reply-To: <20210721094211.69853-1-sgarzare@redhat.com> References: <20210721094211.69853-1-sgarzare@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sgarzare@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=sgarzare@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) DKIMWL_WL_HIGH=-1.474, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , =?utf-8?q?Dan?= =?utf-8?q?iel_P=2E_Berrang=C3=A9?= , Eduardo Habkost , qemu-block@nongnu.org, Stefan Weil , Markus Armbruster , Max Reitz , Paolo Bonzini , Eric Blake , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Changes in preparation for next patches where we add a new parameter not related to the poll mechanism. Let's add two new generic functions (iothread_set_param and iothread_get_param) that we use to set and get IOThread parameters. Signed-off-by: Stefano Garzarella --- iothread.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/iothread.c b/iothread.c index 2c5ccd7367..103679a16b 100644 --- a/iothread.c +++ b/iothread.c @@ -213,7 +213,7 @@ static PollParamInfo poll_shrink_info = { "poll-shrink", offsetof(IOThread, poll_shrink), }; -static void iothread_get_poll_param(Object *obj, Visitor *v, +static void iothread_get_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) { IOThread *iothread = IOTHREAD(obj); @@ -223,7 +223,7 @@ static void iothread_get_poll_param(Object *obj, Visitor *v, visit_type_int64(v, name, field, errp); } -static void iothread_set_poll_param(Object *obj, Visitor *v, +static bool iothread_set_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) { IOThread *iothread = IOTHREAD(obj); @@ -232,17 +232,36 @@ static void iothread_set_poll_param(Object *obj, Visitor *v, int64_t value; if (!visit_type_int64(v, name, &value, errp)) { - return; + return false; } if (value < 0) { error_setg(errp, "%s value must be in range [0, %" PRId64 "]", info->name, INT64_MAX); - return; + return false; } *field = value; + return true; +} + +static void iothread_get_poll_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + + iothread_get_param(obj, v, name, opaque, errp); +} + +static void iothread_set_poll_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + IOThread *iothread = IOTHREAD(obj); + + if (!iothread_set_param(obj, v, name, opaque, errp)) { + return; + } + if (iothread->ctx) { aio_context_set_poll_params(iothread->ctx, iothread->poll_max_ns, From patchwork Wed Jul 21 09:42:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Garzarella X-Patchwork-Id: 12390473 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 845B8C07E9B for ; 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Wed, 21 Jul 2021 09:42:28 +0000 (UTC) Received: from steredhat.redhat.com (ovpn-113-80.ams2.redhat.com [10.36.113.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id 67AAB610A8; Wed, 21 Jul 2021 09:42:22 +0000 (UTC) From: Stefano Garzarella To: Stefan Hajnoczi , qemu-devel@nongnu.org Subject: [PATCH for-6.1? v2 2/3] iothread: add aio-max-batch parameter Date: Wed, 21 Jul 2021 11:42:10 +0200 Message-Id: <20210721094211.69853-3-sgarzare@redhat.com> In-Reply-To: <20210721094211.69853-1-sgarzare@redhat.com> References: <20210721094211.69853-1-sgarzare@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sgarzare@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=sgarzare@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.474, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , =?utf-8?q?Dan?= =?utf-8?q?iel_P=2E_Berrang=C3=A9?= , Eduardo Habkost , qemu-block@nongnu.org, Stefan Weil , Markus Armbruster , Max Reitz , Paolo Bonzini , Eric Blake , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The `aio-max-batch` parameter will be propagated to AIO engines and it will be used to control the maximum number of queued requests. When there are in queue a number of requests equal to `aio-max-batch`, the engine invokes the system call to forward the requests to the kernel. This parameter allows us to control the maximum batch size to reduce the latency that requests might accumulate while queued in the AIO engine queue. If `aio-max-batch` is equal to 0 (default value), the AIO engine will use its default maximum batch size value. Signed-off-by: Stefano Garzarella --- Notes: v2: - s/bacth/batch/ [stefanha] qapi/misc.json | 6 ++++- qapi/qom.json | 7 ++++- include/block/aio.h | 12 +++++++++ include/sysemu/iothread.h | 3 +++ iothread.c | 55 +++++++++++++++++++++++++++++++++++---- monitor/hmp-cmds.c | 2 ++ util/aio-posix.c | 12 +++++++++ util/aio-win32.c | 5 ++++ util/async.c | 2 ++ qemu-options.hx | 8 ++++-- 10 files changed, 103 insertions(+), 9 deletions(-) diff --git a/qapi/misc.json b/qapi/misc.json index 156f98203e..5c2ca3b556 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -86,6 +86,9 @@ # @poll-shrink: how many ns will be removed from polling time, 0 means that # it's not configured (since 2.9) # +# @aio-max-batch: maximum number of requests in a batch for the AIO engine, +# 0 means that the engine will use its default (since 6.1) +# # Since: 2.0 ## { 'struct': 'IOThreadInfo', @@ -93,7 +96,8 @@ 'thread-id': 'int', 'poll-max-ns': 'int', 'poll-grow': 'int', - 'poll-shrink': 'int' } } + 'poll-shrink': 'int', + 'aio-max-batch': 'int' } } ## # @query-iothreads: diff --git a/qapi/qom.json b/qapi/qom.json index 652be317b8..6d5f4a88e6 100644 --- a/qapi/qom.json +++ b/qapi/qom.json @@ -516,12 +516,17 @@ # algorithm detects it is spending too long polling without # encountering events. 0 selects a default behaviour (default: 0) # +# @aio-max-batch: maximum number of requests in a batch for the AIO engine, +# 0 means that the engine will use its default +# (default:0, since 6.1) +# # Since: 2.0 ## { 'struct': 'IothreadProperties', 'data': { '*poll-max-ns': 'int', '*poll-grow': 'int', - '*poll-shrink': 'int' } } + '*poll-shrink': 'int', + '*aio-max-batch': 'int' } } ## # @MemoryBackendProperties: diff --git a/include/block/aio.h b/include/block/aio.h index 807edce9b5..47fbe9d81f 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -232,6 +232,9 @@ struct AioContext { int64_t poll_grow; /* polling time growth factor */ int64_t poll_shrink; /* polling time shrink factor */ + /* AIO engine parameters */ + int64_t aio_max_batch; /* maximum number of requests in a batch */ + /* * List of handlers participating in userspace polling. Protected by * ctx->list_lock. Iterated and modified mostly by the event loop thread @@ -755,4 +758,13 @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, int64_t grow, int64_t shrink, Error **errp); +/** + * aio_context_set_aio_params: + * @ctx: the aio context + * @max_batch: maximum number of requests in a batch, 0 means that the + * engine will use its default + */ +void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch, + Error **errp); + #endif diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h index f177142f16..7f714bd136 100644 --- a/include/sysemu/iothread.h +++ b/include/sysemu/iothread.h @@ -37,6 +37,9 @@ struct IOThread { int64_t poll_max_ns; int64_t poll_grow; int64_t poll_shrink; + + /* AioContext AIO engine parameters */ + int64_t aio_max_batch; }; typedef struct IOThread IOThread; diff --git a/iothread.c b/iothread.c index 103679a16b..ddbbde61f7 100644 --- a/iothread.c +++ b/iothread.c @@ -152,6 +152,24 @@ static void iothread_init_gcontext(IOThread *iothread) iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE); } +static void iothread_set_aio_context_params(IOThread *iothread, Error **errp) +{ + ERRP_GUARD(); + + aio_context_set_poll_params(iothread->ctx, + iothread->poll_max_ns, + iothread->poll_grow, + iothread->poll_shrink, + errp); + if (*errp) { + return; + } + + aio_context_set_aio_params(iothread->ctx, + iothread->aio_max_batch, + errp); +} + static void iothread_complete(UserCreatable *obj, Error **errp) { Error *local_error = NULL; @@ -171,11 +189,7 @@ static void iothread_complete(UserCreatable *obj, Error **errp) */ iothread_init_gcontext(iothread); - aio_context_set_poll_params(iothread->ctx, - iothread->poll_max_ns, - iothread->poll_grow, - iothread->poll_shrink, - &local_error); + iothread_set_aio_context_params(iothread, &local_error); if (local_error) { error_propagate(errp, local_error); aio_context_unref(iothread->ctx); @@ -212,6 +226,9 @@ static PollParamInfo poll_grow_info = { static PollParamInfo poll_shrink_info = { "poll-shrink", offsetof(IOThread, poll_shrink), }; +static PollParamInfo aio_max_batch_info = { + "aio-max-batch", offsetof(IOThread, aio_max_batch), +}; static void iothread_get_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) @@ -271,6 +288,29 @@ static void iothread_set_poll_param(Object *obj, Visitor *v, } } +static void iothread_get_aio_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + + iothread_get_param(obj, v, name, opaque, errp); +} + +static void iothread_set_aio_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + IOThread *iothread = IOTHREAD(obj); + + if (!iothread_set_param(obj, v, name, opaque, errp)) { + return; + } + + if (iothread->ctx) { + aio_context_set_aio_params(iothread->ctx, + iothread->aio_max_batch, + errp); + } +} + static void iothread_class_init(ObjectClass *klass, void *class_data) { UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); @@ -288,6 +328,10 @@ static void iothread_class_init(ObjectClass *klass, void *class_data) iothread_get_poll_param, iothread_set_poll_param, NULL, &poll_shrink_info); + object_class_property_add(klass, "aio-max-batch", "int", + iothread_get_aio_param, + iothread_set_aio_param, + NULL, &aio_max_batch_info); } static const TypeInfo iothread_info = { @@ -337,6 +381,7 @@ static int query_one_iothread(Object *object, void *opaque) info->poll_max_ns = iothread->poll_max_ns; info->poll_grow = iothread->poll_grow; info->poll_shrink = iothread->poll_shrink; + info->aio_max_batch = iothread->aio_max_batch; QAPI_LIST_APPEND(*tail, info); return 0; diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c index 0942027208..e00255f7ee 100644 --- a/monitor/hmp-cmds.c +++ b/monitor/hmp-cmds.c @@ -1893,6 +1893,8 @@ void hmp_info_iothreads(Monitor *mon, const QDict *qdict) monitor_printf(mon, " poll-max-ns=%" PRId64 "\n", value->poll_max_ns); monitor_printf(mon, " poll-grow=%" PRId64 "\n", value->poll_grow); monitor_printf(mon, " poll-shrink=%" PRId64 "\n", value->poll_shrink); + monitor_printf(mon, " aio-max-batch=%" PRId64 "\n", + value->aio_max_batch); } qapi_free_IOThreadInfoList(info_list); diff --git a/util/aio-posix.c b/util/aio-posix.c index 30f5354b1e..2b86777e91 100644 --- a/util/aio-posix.c +++ b/util/aio-posix.c @@ -716,3 +716,15 @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, aio_notify(ctx); } + +void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch, + Error **errp) +{ + /* + * No thread synchronization here, it doesn't matter if an incorrect value + * is used once. + */ + ctx->aio_max_batch = max_batch; + + aio_notify(ctx); +} diff --git a/util/aio-win32.c b/util/aio-win32.c index 168717b51b..d5b09a1193 100644 --- a/util/aio-win32.c +++ b/util/aio-win32.c @@ -440,3 +440,8 @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, error_setg(errp, "AioContext polling is not implemented on Windows"); } } + +void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch, + Error **errp) +{ +} diff --git a/util/async.c b/util/async.c index 9a41591319..6f6717a34b 100644 --- a/util/async.c +++ b/util/async.c @@ -554,6 +554,8 @@ AioContext *aio_context_new(Error **errp) ctx->poll_grow = 0; ctx->poll_shrink = 0; + ctx->aio_max_batch = 0; + return ctx; fail: g_source_destroy(&ctx->source); diff --git a/qemu-options.hx b/qemu-options.hx index 0c9ddc0274..99ed5ec5f1 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -5301,7 +5301,7 @@ SRST CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB - ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink`` + ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch`` Creates a dedicated event loop thread that devices can be assigned to. This is known as an IOThread. By default device emulation happens in vCPU threads or the main event loop thread. @@ -5337,7 +5337,11 @@ SRST the polling time when the algorithm detects it is spending too long polling without encountering events. - The polling parameters can be modified at run-time using the + The ``aio-max-batch`` parameter is the maximum number of requests + in a batch for the AIO engine, 0 means that the engine will use + its default. + + The IOThread parameters can be modified at run-time using the ``qom-set`` command (where ``iothread1`` is the IOThread's ``id``): From patchwork Wed Jul 21 09:42:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Garzarella X-Patchwork-Id: 12390467 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11F40C07E9B for ; Wed, 21 Jul 2021 09:45:05 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8F45B6120E for ; Wed, 21 Jul 2021 09:45:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F45B6120E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36136 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m68ml-0008Lm-MM for qemu-devel@archiver.kernel.org; Wed, 21 Jul 2021 05:45:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44068) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m68kT-0005uZ-Hx for qemu-devel@nongnu.org; Wed, 21 Jul 2021 05:42:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:27011) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m68kR-0003MN-Mb for qemu-devel@nongnu.org; Wed, 21 Jul 2021 05:42:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626860559; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+Y0MVXSBI9lM9tZrqQKyrXak/hxN23BmyOZhZ8bm93g=; b=aXkAy2QWfV5guB/lhD0fDM+mQI94hx4amNcnFRY775rdWQ2IrYyLP/X3Fvh4tL17JtInY7 n+LgWbmUBgvZjT8IG0w6geGARRjQj+K+Y+Ho+sUxif5MC0r1BjwFtgsZ5EFtZYcdDsP33X 5evZi812pvaeyTzmnn13lCQtWIKdFlU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-566-1PnUgoPbPAKtaApy1kh_8A-1; Wed, 21 Jul 2021 05:42:35 -0400 X-MC-Unique: 1PnUgoPbPAKtaApy1kh_8A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B33388C7AC1; Wed, 21 Jul 2021 09:42:34 +0000 (UTC) Received: from steredhat.redhat.com (ovpn-113-80.ams2.redhat.com [10.36.113.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id A0C2E60E1C; Wed, 21 Jul 2021 09:42:28 +0000 (UTC) From: Stefano Garzarella To: Stefan Hajnoczi , qemu-devel@nongnu.org Subject: [PATCH for-6.1? v2 3/3] linux-aio: limit the batch size using `aio-max-batch` parameter Date: Wed, 21 Jul 2021 11:42:11 +0200 Message-Id: <20210721094211.69853-4-sgarzare@redhat.com> In-Reply-To: <20210721094211.69853-1-sgarzare@redhat.com> References: <20210721094211.69853-1-sgarzare@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sgarzare@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=170.10.133.124; envelope-from=sgarzare@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.474, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , Kevin Wolf , =?utf-8?q?Dan?= =?utf-8?q?iel_P=2E_Berrang=C3=A9?= , Eduardo Habkost , qemu-block@nongnu.org, Stefan Weil , Markus Armbruster , Max Reitz , Paolo Bonzini , Eric Blake , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" When there are multiple queues attached to the same AIO context, some requests may experience high latency, since in the worst case the AIO engine queue is only flushed when it is full (MAX_EVENTS) or there are no more queues plugged. Commit 2558cb8dd4 ("linux-aio: increasing MAX_EVENTS to a larger hardcoded value") changed MAX_EVENTS from 128 to 1024, to increase the number of in-flight requests. But this change also increased the potential maximum batch to 1024 elements. When there is a single queue attached to the AIO context, the issue is mitigated from laio_io_unplug() that will flush the queue every time is invoked since there can't be others queue plugged. Let's use the new `aio-max-batch` IOThread parameter to mitigate this issue, limiting the number of requests in a batch. We also define a default value (32): this value is obtained running some benchmarks and it represents a good tradeoff between the latency increase while a request is queued and the cost of the io_submit(2) system call. Signed-off-by: Stefano Garzarella --- Notes: v2: - limit the batch with the number of available events [stefanha] block/linux-aio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/linux-aio.c b/block/linux-aio.c index 3c0527c2bf..0dab507b71 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -28,6 +28,9 @@ */ #define MAX_EVENTS 1024 +/* Maximum number of requests in a batch. (default value) */ +#define DEFAULT_MAX_BATCH 32 + struct qemu_laiocb { Coroutine *co; LinuxAioState *ctx; @@ -351,6 +354,10 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset, LinuxAioState *s = laiocb->ctx; struct iocb *iocbs = &laiocb->iocb; QEMUIOVector *qiov = laiocb->qiov; + int64_t max_batch = s->aio_context->aio_max_batch ?: DEFAULT_MAX_BATCH; + + /* limit the batch with the number of available events */ + max_batch = MIN_NON_ZERO(MAX_EVENTS - s->io_q.in_flight, max_batch); switch (type) { case QEMU_AIO_WRITE: @@ -371,7 +378,7 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset, s->io_q.in_queue++; if (!s->io_q.blocked && (!s->io_q.plugged || - s->io_q.in_flight + s->io_q.in_queue >= MAX_EVENTS)) { + s->io_q.in_queue >= max_batch)) { ioq_submit(s); }