From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC9BCC77B70 for ; Mon, 17 Apr 2023 12:44:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231264AbjDQMo4 (ORCPT ); Mon, 17 Apr 2023 08:44:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231222AbjDQMou (ORCPT ); Mon, 17 Apr 2023 08:44:50 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8056E6; Mon, 17 Apr 2023 05:44:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1681735489; x=1713271489; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=y/esuIhc93Jp7lxKz3B0zEndGBlU9SQYN2Zc+WRiBI4=; b=aC3W/gRrGmSM4EGAfg9/g+CnS21TGwon1u2GEwboDuwTsGz8hYGSI1Eq P0u0A0mF41stSrsq83TfsXlKiwF1mpVyx7RJRgfCFjVV21qeO4iRdaAKi 0m8Q6LVsfMtHHDs27sDZlze5myeEYWqJrAfM6PF94ibZboZWIr95CMC2o Cp0H01xXhRnoIFixuDvX64nK2MJjafIAT9Q5OgxSAH2i/FAdDWAt0Nirs k8HCcIA4rpgvFIEMNdzy8SYnI1MHlObCArlFEr4VGGLWUfsdEMF/sHC1b MBkXbzelpps66rf3y5COkhCbttA9a4X8Zk8FSeMXPxb3Mc0TKvZCgVDaH g==; X-IronPort-AV: E=McAfee;i="6600,9927,10682"; a="346729368" X-IronPort-AV: E=Sophos;i="5.99,204,1677571200"; d="scan'208";a="346729368" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Apr 2023 05:44:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10682"; a="834407213" X-IronPort-AV: E=Sophos;i="5.99,204,1677571200"; d="scan'208";a="834407213" Received: from lkp-server01.sh.intel.com (HELO b613635ddfff) ([10.239.97.150]) by fmsmga001.fm.intel.com with ESMTP; 17 Apr 2023 05:44:45 -0700 Received: from kbuild by b613635ddfff with local (Exim 4.96) (envelope-from ) id 1poODs-000cMF-0V; Mon, 17 Apr 2023 12:44:44 +0000 Date: Mon, 17 Apr 2023 20:44:41 +0800 From: kernel test robot To: wenyang.linux@foxmail.com, Alexander Viro , Jens Axboe , Christian Brauner Cc: oe-kbuild-all@lists.linux.dev, Wen Yang , Christoph Hellwig , Dylan Yudaken , David Woodhouse , Paolo Bonzini , Fu Wei , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] eventfd: support delayed wakeup for non-semaphore eventfd to reduce cpu utilization Message-ID: <202304172058.piI49JCE-lkp@intel.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, kernel test robot noticed the following build warnings: [auto build test WARNING on vfs-idmapping/for-next] [also build test WARNING on linus/master v6.3-rc7] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/wenyang-linux-foxmail-com/eventfd-support-delayed-wakeup-for-non-semaphore-eventfd-to-reduce-cpu-utilization/20230416-193353 base: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping.git for-next patch link: https://lore.kernel.org/r/tencent_AF886EF226FD9F39D28FE4D9A94A95FA2605%40qq.com patch subject: [PATCH] eventfd: support delayed wakeup for non-semaphore eventfd to reduce cpu utilization reproduce: # https://github.com/intel-lab-lkp/linux/commit/ea9214e265bae223a795f144d6ddcac65e8e2084 git remote add linux-review https://github.com/intel-lab-lkp/linux git fetch --no-tags linux-review wenyang-linux-foxmail-com/eventfd-support-delayed-wakeup-for-non-semaphore-eventfd-to-reduce-cpu-utilization/20230416-193353 git checkout ea9214e265bae223a795f144d6ddcac65e8e2084 make menuconfig # enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS make htmldocs If you fix the issue, kindly add following tag where applicable | Reported-by: kernel test robot | Link: https://lore.kernel.org/oe-kbuild-all/202304172058.piI49JCE-lkp@intel.com/ All warnings (new ones prefixed by >>): >> Documentation/admin-guide/sysctl/fs.rst:74: WARNING: Title underline too short. vim +74 Documentation/admin-guide/sysctl/fs.rst 72 73 eventfd_wakeup_delay_msec > 74 ------------------ 75 Frequent writing of an eventfd can also lead to frequent wakeup of the peer 76 read process, resulting in significant cpu overhead. 77 How ever for the NON SEMAPHORE eventfd, if it's counter has a nonzero value, 78 then a read(2) returns 8 bytes containing that value, and the counter's value 79 is reset to zero. 80 So it coule be optimized as follows: N event_writes vs ONE event_read. 81 By adding a configurable delay after eventfd_write, these unnecessary wakeup 82 operations are avoided. 83 The max value is 100 ms. 84 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests