{"id":2227505,"url":"http://patchwork.ozlabs.org/api/1.1/covers/2227505/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/cover/20260423195918.661299-1-jhkim@linux.ibm.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.1/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260423195918.661299-1-jhkim@linux.ibm.com>","date":"2026-04-23T19:59:15","name":"[v5,0/3] improve aio-polling efficiency","submitter":{"id":91012,"url":"http://patchwork.ozlabs.org/api/1.1/people/91012/?format=json","name":"Jaehoon Kim","email":"jhkim@linux.ibm.com"},"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/cover/20260423195918.661299-1-jhkim@linux.ibm.com/mbox/","series":[{"id":501240,"url":"http://patchwork.ozlabs.org/api/1.1/series/501240/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501240","date":"2026-04-23T19:59:15","name":"improve aio-polling efficiency","version":5,"mbox":"http://patchwork.ozlabs.org/series/501240/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/covers/2227505/comments/","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=bsfIcZf2;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc\n :content-transfer-encoding:date:from:message-id:mime-version\n :subject:to; s=pp1; bh=ahhCUDaFRHbPzr71XPzfQgNefJBpuP6TRTvpbqK1j\n yM=; b=bsfIcZf2Mk+l/JoFTyrsIDde1Q/L/mXsiJpoiIhHsZJuaGk5OY37X+wyr\n DUPwtKBNGwmf7obKc7iy5X4YrUcxXsAAooBUrZZisaY2TslgR+R4acNKvEH+TVOL\n 2ogWaMY8n0veSMT+tGDQHlPxzv8FPhaaETg2lprCED+WsDxQj7VJrXeVpbC+xYce\n ms5DPLAv7Yx9CBcNn67AZBS2ggUjz4NUky2oGr6AD1tX07b5RKCL4mvp/bsDQHni\n ZTrFsRvTR9W92hqSKR3KaNYQ8Ms+RI4yP0slwPUulH0iXQhUA0ytjJt6i41L8MfD\n XKf0rSnXEMzGxt9oL4OZJFTTxaTmg==","From":"Jaehoon Kim ","To":"qemu-devel@nongnu.org, qemu-block@nongnu.org","Cc":"pbonzini@redhat.com, stefanha@redhat.com, fam@euphon.net,\n armbru@redhat.com, eblake@redhat.com, berrange@redhat.com,\n eduardo@habkost.net, dave@treblig.org, sw@weilnetz.de,\n mjrosato@linux.ibm.com, farman@linux.ibm.com,\n Jaehoon Kim ","Subject":"[PATCH v5 0/3] improve aio-polling efficiency","Date":"Thu, 23 Apr 2026 14:59:15 -0500","Message-ID":"<20260423195918.661299-1-jhkim@linux.ibm.com>","X-Mailer":"git-send-email 2.43.0","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-TM-AS-GCONF":"00","X-Proofpoint-GUID":"oQKc6Stj115SwIsGZ-APviHRT3_heYpH","X-Proofpoint-Spam-Details-Enc":"AW1haW4tMjYwNDIzMDE5MyBTYWx0ZWRfX+oTYUIicrfeE\n OvHul+pML5aipCYweDI2/6imFPnIjtQY7AwuSX1LzJ4bsvjOtoxGne/bDyxHKxnmZpm+2IhgMI2\n OO00uAjppAv0v9+KE8nwjYQ1qoIyls96xO/6QJ7Tqyhz9SiXHIDm08o/zI9jqkCyiSwoXQHzcgQ\n s9/1CN+VC0T84PHWsxct1OQBi6C0IwnMiWFC8Rd0iG05iknTFoLvmJDcaNn/xP4Ri/jV8FtEbC8\n 5QYSuKGXU2SVqDegKRqW2ylt90fPqiqHbmy+BwQEVs21v6sjxUL/6IgG+aB1/8dnGn67lAWZxLC\n LDpNGE/xqSmPErndaPrO7bd5TN952ZDXbX8++F7XQ1gLHR3Drmp3iiN7KgEXmqQWkv0InS2MjN2\n jlO4tsoxjz+V5Af62qpLc4qptQxhFrqOBAd4YQ93fo9HuoEstvBjXc9PA7DoxqzvFmiQAwytEGb\n Fal7KzUeHpYvob5J4Wg==","X-Authority-Analysis":"v=2.4 cv=a6kAM0SF c=1 sm=1 tr=0 ts=69ea7a1c cx=c_pps\n a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17\n a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22\n a=V8glGbnc2Ofi9Qvn3v5h:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8\n a=-wZDFzhax2tZ4RQJR_4A:9","X-Proofpoint-ORIG-GUID":"oQKc6Stj115SwIsGZ-APviHRT3_heYpH","X-Proofpoint-Virus-Version":"vendor=baseguard\n engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49\n definitions=2026-04-23_03,2026-04-21_02,2025-10-01_01","X-Proofpoint-Spam-Details":"rule=outbound_notspam policy=outbound score=0\n malwarescore=0 suspectscore=0 spamscore=0 adultscore=0 bulkscore=0\n lowpriorityscore=0 impostorscore=0 clxscore=1015 phishscore=0\n priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc=\n route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000\n definitions=main-2604230193","Received-SPF":"pass client-ip=148.163.158.5; envelope-from=jhkim@linux.ibm.com;\n helo=mx0b-001b2d01.pphosted.com","X-Spam_score_int":"-26","X-Spam_score":"-2.7","X-Spam_bar":"--","X-Spam_report":"(-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7,\n RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001,\n 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":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Dear all,\n\nThis is v5 of the patch series to refine aio_poll adaptive polling\nlogic for better CPU efficiency.\n\nv1: https://lore.kernel.org/qemu-devel/20260113174824.464720-1-jhkim@linux.ibm.com/\nv2: https://lore.kernel.org/qemu-devel/20260323135451.579655-1-jhkim@linux.ibm.com/\nv3: https://lore.kernel.org/qemu-devel/20260405200735.3075407-1-jhkim@linux.ibm.com/\nv4: https://lore.kernel.org/qemu-devel/20260412215011.326196-1-jhkim@linux.ibm.com/\n\nChanges in v5:\n- Patch 3/3: Fixed QAPI documentation based on review feedback:\n * qapi/misc.json: Removed the sentence about returning poll-weight=0\n since query-iothreads never returns 0 for this field.\n * qemu-options.hx: Enhanced poll-weight parameter documentation to\n match the detail level in qom.json, including information about\n default value and typical value examples.\n\nChanges in v4:\n- Patch 2/3: Added detailed validation tables showing poll.ns statistics\n across different poll_weight values (1-5) for SSD randread/randwrite\n workloads to demonstrate algorithm behavior and justify poll_weight=3\n as the optimal default.\n\n- Patch 3/3: Fixed commit message to correctly reference\n adjust_polling_time() instead of the removed grow_polling_time()\n and shrink_polling_time() functions from v2.\n\nChanges in v3:\n- Patch 1/3: Removed timeout check in aio_poll() as suggested by\n Stefan Hajnoczi.\n\n- Patch 2/3: Major refactoring based on review feedback:\n * Removed has_event and renamed poll_idle_timeout to\n last_dispatch_timestamp from AioHandler structure to identify\n active handlers.\n * Merged grow_polling_time() and shrink_polling_time() into single\n adjust_polling_time() function to simplify code review, with no\n functional changes.\n * Renamed adjust_block_ns() to update_handler_poll_times()\n * Modified remove_idle_poll_handlers() to use last_dispatch_timestamp\n directly instead of checking poll_idle_timeout\n * Updated commit message\n\n- Patch 3/3: Enhanced parameter handling:\n * Moved IOTHREAD_POLL_*_DEFAULT constants to iothread.h header\n * Added validation for poll-weight range [0, 63] in iothread.c\n * Added the divide-by-0 protection in aio_context_set_poll_params()\n * Updated QAPI version from 10.2 to 11.1\n * Enhanced qom.json documentation for poll-weight values\n\nThis series reduces CPU usage in aio_poll adaptive polling by ~10%\nwith minimal throughput impact (~2%). Tested on s390x with various\nworkloads.\n\nTesting details:\n\nInitial testing (Fedora 42, 16 virtio-blk devices, FCP multipath):\n - Throughput: -3% to -8% (1 iothread), -2% to -5% (2 iothreads)\n - CPU usage: -10% to -25% (1 iothread), -7% to -12% (2 iothreads)\n\nAdditional validation (RHEL 10.1 + QEMU 10.0.0, FCP/FICON, 1-8 iothreads):\n - Throughput: -2.2% (weight=3), -2.4% (weight=2)\n - CPU usage: -9.4% (weight=3), -10.9% (weight=2)\n\nWeight=3 selected for slightly better throughput while maintaining\nsubstantial CPU savings.\n\nBest regards,\nJaehoon Kim\n\nJaehoon Kim (3):\n aio-poll: avoid unnecessary polling time computation\n aio-poll: refine iothread polling using weighted handler intervals\n qapi/iothread: introduce poll-weight parameter for aio-poll\n\n include/qemu/aio.h | 7 +-\n include/system/iothread.h | 18 ++++\n iothread.c | 47 +++++++---\n monitor/hmp-cmds.c | 1 +\n qapi/misc.json | 6 ++\n qapi/qom.json | 10 +-\n qemu-options.hx | 8 +-\n tests/unit/test-nested-aio-poll.c | 2 +-\n util/aio-posix.c | 148 ++++++++++++++++++------------\n util/aio-posix.h | 2 +-\n util/aio-win32.c | 3 +-\n util/async.c | 2 +\n 12 files changed, 176 insertions(+), 78 deletions(-)"}