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{ "id": 2220016, "url": "http://patchwork.ozlabs.org/api/1.2/covers/2220016/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/cover/20260405200735.3075407-1-jhkim@linux.ibm.com/", "project": { "id": 14, "url": "http://patchwork.ozlabs.org/api/1.2/projects/14/?format=api", "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": "", "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260405200735.3075407-1-jhkim@linux.ibm.com>", "list_archive_url": null, "date": "2026-04-05T20:07:31", "name": "[v3,0/3] improve aio-polling efficiency", "submitter": { "id": 91012, "url": "http://patchwork.ozlabs.org/api/1.2/people/91012/?format=api", "name": "Jaehoon Kim", "email": "jhkim@linux.ibm.com" }, "mbox": "http://patchwork.ozlabs.org/project/qemu-devel/cover/20260405200735.3075407-1-jhkim@linux.ibm.com/mbox/", "series": [ { "id": 498805, "url": "http://patchwork.ozlabs.org/api/1.2/series/498805/?format=api", "web_url": "http://patchwork.ozlabs.org/project/qemu-devel/list/?series=498805", "date": "2026-04-05T20:07:32", "name": "improve aio-polling efficiency", "version": 3, "mbox": "http://patchwork.ozlabs.org/series/498805/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/covers/2220016/comments/", "headers": { "Return-Path": "<qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org>", "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=Mlate4L1;\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=MUtclOe3kKJf2/41pfZixUNYP6lmJcGZUZiD+Rcfy\n 0k=; b=Mlate4L1YiWc0gQPg7IvvGp2YgiyABrXb3EwzdMonM9iIPzZI5h2yF0x5\n 8r2JYqThVv2R7mBLH+3ZOg7VwDvIeXaVatB8x5b1TZq3PPEshjffjwyTbAooYEtb\n Rj9MGHPqaNaR80oTW8GcaVf+hipWIKpQ52nM5AeqeAJm3REzG2AoEAS9BH83sSLC\n 6hO8My/fBBT13TgAmlCdDRuh8k2/navKk9Iqkt2RcSA2J4v6rqCZ/34IzgBl6rOH\n dqdnKhKB8UjpM4Dd5OFU+9ZA71b4Q0IJmv/q+xj39a4pMBf2fyyvX/6xmJ4ukfA4\n 0I+LCcrzZ3LctXjnmH0UmtGRVXVfw==", "From": "Jaehoon Kim <jhkim@linux.ibm.com>", "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 <jhkim@linux.ibm.com>", "Subject": "[PATCH v3 0/3] improve aio-polling efficiency", "Date": "Sun, 5 Apr 2026 15:07:31 -0500", "Message-ID": "<20260405200735.3075407-1-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": "k-pIEU_5TZO3w7ffQLwm5aPgDsLWjbeS", "X-Proofpoint-ORIG-GUID": "k-pIEU_5TZO3w7ffQLwm5aPgDsLWjbeS", "X-Authority-Analysis": "v=2.4 cv=bLYb4f+Z c=1 sm=1 tr=0 ts=69d2c10d cx=c_pps\n a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17\n a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22\n a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8\n a=LaYcTpCPktSTTGNkxp8A:9", "X-Proofpoint-Spam-Details-Enc": "AW1haW4tMjYwNDA1MDIwNiBTYWx0ZWRfX+I6Fe1VZXnp4\n 7dLnCk9HTOC51gB4NKPhmTBhKMlRbaM699hKhCxzBfBAJYfkjaoFeKtn73XZu77Eble9OGT6woM\n nm/GDi0kn3H1mhw30XHxc43GuZD1qgpQLr1j6wVXbmOAj74N2epqiCDg6cHHPoHYZ95CtXna2lm\n AZ1bkVOh+RlmeDVsh/DzhQyBi9nLivFiT6l1+d7F0B5eEKVSdlRJ0PmZ54k2BhQFPCAicrCiIlG\n D594U2NT5s8nD5KfDZ0SiCjx8xGgB+weRXNDHUS2D3T3MtlLltCBkYigmi0ugHlAEYJ9QUBRv7v\n BYr1V7YO8rm0AEQP0DUn6LFd6hZwmqXbAdi95WDfTXsMyOg6H8bm7372DCV4txKB9z2RtnIiSFO\n c+w30FY8s6CshyTqY1p9SDX0wntKvZ+QQYNHHaAWv1b+H/0373Re6JfoqxsMW5S9jZ1jYZGCXJI\n IaT5h64Ti49RwZxD93w==", "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=2026-04-05_06,2026-04-03_01,2025-10-01_01", "X-Proofpoint-Spam-Details": "rule=outbound_notspam policy=outbound score=0\n clxscore=1015 adultscore=0 suspectscore=0 phishscore=0 bulkscore=0\n spamscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0\n impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc=\n route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001\n definitions=main-2604050206", "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,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n 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": "qemu development <qemu-devel.nongnu.org>", "List-Unsubscribe": "<https://lists.nongnu.org/mailman/options/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>", "List-Archive": "<https://lists.nongnu.org/archive/html/qemu-devel>", "List-Post": "<mailto:qemu-devel@nongnu.org>", "List-Help": "<mailto:qemu-devel-request@nongnu.org?subject=help>", "List-Subscribe": "<https://lists.nongnu.org/mailman/listinfo/qemu-devel>,\n <mailto:qemu-devel-request@nongnu.org?subject=subscribe>", "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 v3 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/\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 | 7 ++\n qapi/qom.json | 10 +-\n qemu-options.hx | 7 +-\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(-)" }