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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-48fe9ea183fsi6061469f8f.36.2026.11.04.13.35.14 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 13:35:14 -0800 (PST) Received-SPF: pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=Jr4nnQ31; spf=pass (google.com: domain of khorenko@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=khorenko@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Message-Id:Date:From:Subject:Content-Type: MIME-Version; bh=eKIMTyLcNMEn8RSxxIzGj7zvojS8wbSeBP/kvH8+5JQ=; b=Jr4nnQ31RZQC 9EyuhrL9c0yMGw7qKK/FJ8iTfFPja8vPQOmw/ExBkulsTLjLmcd3Z78+fsG6nyhDbDys+24F1wH5I gLHDMfuYD3dWe3dVxW/DR3QMZ3l8Cd2gndlh9iaUCUJ42E08IOgJnkGGTDyw9OU114yC4mCJpkM3F n7SmQGtdRbl74S7YtyxWMDhTLlNBq+OdAHf2pDEQCF2Vlxs3+ppRckNdutU2A5iT9wvCoYlzcgthW 5kMKt24fkWvnCkP+FzobwDLlPHq8qmMMverAfCEPlfxuzl8ayV5ec2xthdjkUhXQfSl8+HT6WxhAT DswmsQQqzgIxU+JzODljiw==; Received: from ch-demo-asa.virtuozzo.com ([130.117.225.8] helo=f0.sw.ru) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1xOiZY-00248s-17; Wed, 04 Nov 2026 22:35:12 +0100 MIME-Version: 1.0 From: Konstantin Khorenko To: Andrey Zhadchenko In-Reply-To: <20261029140346.465768-1-andrey.zhadchenko@virtuozzo.com> References: <20261029140346.465768-1-andrey.zhadchenko@virtuozzo.com> Date: Wed, 04 Nov 2026 22:35:09 +0100 Message-Id: <179382810902.2794215.4545739354769906012.b4-review@b4> X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1962; i=khorenko@virtuozzo.com; h=from:subject:message-id; bh=TSz12DXeCjkoNoICw+S5LVW9HMZbcFQziNjJxvmIzLI=; b=owEBbQKS/ZANAwAKAVGWCkf5YVwqAcsmYgBq66UOypztRYpSPE6mzKh49Uc4e6ishkSLYJh/f XDOSWtNn5KJAjMEAAEKAB0WIQRWD23IPcXT0GO9CCxRlgpH+WFcKgUCauulDgAKCRBRlgpH+WFc KuCpEACLsxE+jEZTNrTNhnRAhVqinbFCACueDFV4wnNCPYp45r8QrZCPNc/ZLHSBk0oy7V0GFqy blgjCxJeCyNsarFUcRUVePa3hryMOsjdIP4vuSCx2BlKBUiZKnyVL+BLKJdzjsnc7nmXD+V9zkE G77+qBNWc7U6BNLd9C4ADdnRBDvPjcuVZyOBhYMBo3eMYkaXJHEdknyWIc/onwOoJ1BwksAl8GI eW00AsuU//AuLC9Qg7FJq+0zycm7UnqnMOciIvgiAxQCv/8DVWRnq2ZW5ZJ1s3IPgKLpY0yr2ie O3RCLPYe6L3cE6v2bxEEOiONsBVt3qk6fTZRihtwv3yCMHq2+bizPqixWOfTShOtaQwHKOb8Lb5 ojNH+tTchpaMcs7ZReK9ybwUpHkUSfCPmzT2EsxP+vg2/RewJyssqpqRrw6zr84HWqzjHGj1S2L z9o5Th39GQXOfukh56DKTRQOdftl6xXVzZo6GH5F1vz29mExz5JZddbwDb3hqwPeR+6dinltxNp Gv8c34DGQN+KIKfAANSmfvOpGs9UCsi+cpNmbQZGgQTFmjJSL+h3MLIcyc8cDUaUj6WHM/GuODB 0/cW6s4+mceXITInzj/6koGyWi7k2wGsvhGBR+ZFqTZhU+EjN/tM/NWquB/tq90UN+p9zZYnCYb ljdfWpSJ1rO1fbQ== X-Developer-Key: i=khorenko@virtuozzo.com; a=openpgp; fpr=560F6DC83DC5D3D063BD082C51960A47F9615C2A X-OZ-Fwd: true Cc: devel@openvz.org Subject: Re: [Devel] [PATCH 0/7] drivers/md/dm-qcow2: per-qio fast path X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org I won't apply this version, please send v2 with the changes below. On Thu, 29 Oct 2026 17:03:39 +0300, Andrey Zhadchenko wrote: > dm-qcow2 processes every request consequentially in a single kwork. > Unfortunately this introduces latency and cpu-bound limits. This > patchset addresses the problem by laying per-qio tasks foundation: > qios can be executed in parallel on the same workqueue. For now cover > only requests with metadata fully allocated. What to change for v2: 1. Patches 2 and 5, code: a fast-path write can miss the wbd of the L2 page that maps it, and then it is acked before that L2 entry is on disk. Handle MD_WRITEBACK in perform_rw_mapped() the way parse_l2() does. 2. Patch 3, code: stop the fast path before the R1/R2 lookup in parse_metadata(), it never needs those pages. 3. Patch 1, commit message: say what fails today and add a Fixes tag for 412d5a4f7bf1b ("dm/dm-qcow2: add llseek_hole"). 4. Patch 7, code and message: bound the drain loop, fix the sentence about re-queued qios, say that the fast path is now serial per submitting CPU. 5. Patches 6 and 7, commit messages: move the measured numbers into this thread. 6. Patch 4, code: update the QLIST_EMBEDDED comment. 7. Open remarks from the thread, please answer or fix them in v2: Sashiko on patch 1 (unbounded retry) and patch 5 (list_add order), Alexander on patch 3 (typo, magic 2) and patch 6 (swap 6 and 7). 8. Cover letter of v2: - "consequentially" becomes "sequentially"; - not only fully allocated requests go fast: reads of unallocated or lower-delta clusters and partial discards do too, say that; - mention DM_TARGET_NOWAIT and the per-cpu batching. Details on each item are in the replies to the patches. Alexander's Reviewed-by should not be carried over to v2 as is, item 1 changes the code he reviewed. -- Konstantin Khorenko, Virtuozzo Linux Kernel Team _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel