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X-CSE-ConnectionGUID: nUrP2XsdQtWRzq6MHIoyBA== X-CSE-MsgGUID: Joj5hH1qSXOus9cjz2vGVA== X-IronPort-AV: E=McAfee;i="6800,10657,11561"; a="71985426" X-IronPort-AV: E=Sophos;i="6.18,287,1751266800"; d="scan'208";a="71985426" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2025 22:52:33 -0700 X-CSE-ConnectionGUID: ey1wUJiRRRmHLQLcgAPe8Q== X-CSE-MsgGUID: borv5jnjTHC3J6hNV2upxA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,287,1751266800"; d="scan'208";a="180973917" Received: from alc-skl-a23.sh.intel.com (HELO [10.239.53.6]) ([10.239.53.6]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2025 22:52:30 -0700 Message-ID: <93f7e2ad-563b-4db5-bab6-4ce2e994dbae@linux.intel.com> Date: Tue, 23 Sep 2025 13:11:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/readahead: Skip fully overlapped range To: Andrew Morton Cc: Matthew Wilcox , Nanhai Zou , Gang Deng , Tianyou Li , Vinicius Gomes , Tim Chen , Chen Yu , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Roman Gushchin References: <20250923035946.2560876-1-aubrey.li@linux.intel.com> <20250922204921.898740570c9a595c75814753@linux-foundation.org> Content-Language: en-US From: Aubrey Li In-Reply-To: <20250922204921.898740570c9a595c75814753@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: szti4t97jomoe5cw55mxxrcwqp6tjqd9 X-Rspam-User: X-Rspamd-Queue-Id: 6D169120004 X-Rspamd-Server: rspam10 X-HE-Tag: 1758606754-188070 X-HE-Meta: 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 urgcCh8y +97af0ygE6w/gwuXTZrZtCYBwzw+W8tg4M9HfMYzx6kXi/ktRFtF4H5gYJZWPAzqe1AyeTTTwqRrAyH8zDN6qN27jqyDDSmeM2TSr8rwpfI6w2+pmNztKUUr0+8LAOt46u7xNbcC3EkEFsvUoGFh4O8BLx/szFWPZdmuy+dcrgwMvAXCky914wTsE+b/no5XCr9oU0UXKvHSfmla+zaWUmX7T0qGSqhLxogp4 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/23/25 11:49, Andrew Morton wrote: > On Tue, 23 Sep 2025 11:59:46 +0800 Aubrey Li wrote: > >> RocksDB sequential read benchmark under high concurrency shows severe >> lock contention. Multiple threads may issue readahead on the same file >> simultaneously, which leads to heavy contention on the xas spinlock in >> filemap_add_folio(). Perf profiling indicates 30%~60% of CPU time spent >> there. >> >> To mitigate this issue, a readahead request will be skipped if its >> range is fully covered by an ongoing readahead. This avoids redundant >> work and significantly reduces lock contention. In one-second sampling, >> contention on xas spinlock dropped from 138,314 times to 2,144 times, >> resulting in a large performance improvement in the benchmark. >> >> w/o patch w/ patch >> RocksDB-readseq (ops/sec) >> (32-threads) 1.2M 2.4M > > On which kernel version? In recent times we've made a few readahead > changes to address issues with high concurrency and a quick retest on > mm.git's current mm-stable branch would be interesting please. > I'm on v6.16.7. Thanks Andrew for the information, let me check with mm.git. Thanks, -Aubrey