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b=i9X4BeG7QM21TD20y696jUkaoliMwB0q+MPMMT5ynyvu5uGDczI20fqrVZbtqmE6X /KLl0SyQf0BGfLKKR/X9R7/rTJZzenAjoXQZxBTfZAw8jkWtyQK0b8pQkOPHF+Pc0V Fy6M+EQ53U5oYELoqLbNMfKhMqtPBRu/xfpV2dmjr5Mv69WjICprlWau08ueZuigkv o5fQEBGXoIC/LwzsmaQHk8ss13KwaijqZrrZN9OmGMGShA7oD2f0kX3dPxuMkbivIm DGkDNc4Ne3sJUY6lJWVFw4x47Gf1v/3UvXhD0ZfLX+8Wf08f9b4g5FBH4iofUmOhfR hwWlmUUoz82vw== Message-ID: Date: Tue, 17 Mar 2026 10:21:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: "Vlastimil Babka (SUSE)" Subject: Re: [PATCH v3] iomap: add allocation cache for iomap_dio Content-Language: en-US To: Christoph Hellwig , changfengnan Cc: Dave Chinner , Harry Yoo , Hao Li , guzebing , brauner@kernel.org, djwong@kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, guzebing@bytedance.com, syzbot@syzkaller.appspotmail.com, linux-mm@kvack.org References: <20260115021108.1913695-1-guzebing1612@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 11C5A180006 X-Rspamd-Server: rspam08 X-Stat-Signature: myr85zcjqb4hy9enkkgmimq7tu64j8dq X-HE-Tag: 1773739273-861931 X-HE-Meta: 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 sstGwxDB dhyOSY+FXb8ibYncD/x1ZUk7uOkzfSI8g0DqHDm3dA7Xc4xZ6k8+TrcWPbuZJf5d9Y0f82Z5P0t8LFZb1NWIHKEbb+F7xDxvI1/qmC82ZNjb3am50fcil5aVaTAeltQO6kGxP9axX7M7ndsL1pXTL/tpmEuxCFFYgKQL5aGfoXahVVJbEC4Ilr3FAi7DJfSXDsNsGO/i3xVXYV9NoqGIYD4XaCc2bJyRzd6uuhxRMBTjNFvn+sH3cbMik4m7aTtEji5+XWUgbAHVX53pFE+Nca1YBoJluHqn3AsBgz5OG2TLbPjnNyPGPBEFBxyPwZl1Oe5aU6T9d4ocS4GU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/17/26 10:12, Christoph Hellwig wrote: > On Tue, Mar 17, 2026 at 04:33:24PM +0800, changfengnan wrote: >> > IO is not my area but getting from 1.19M to 1.20M doesn't look like it's >> > worth the custom code? (possibly from 1.17M to 1.20M it also wasn't). >> Yes, at least for now, there’s no need for a per-CPU. >> It might be better to replace kmalloc with a new cache, but my tests so far >> haven’t shown any performance improvements.  I’ll look into it further. > > Does using a kmem_cache help? That should generally be a nice win > anyway due to keeping the objects together. I think that's exactly what "It might be better to replace kmalloc with a new cache" meant, and apparently with no improvements. You might want to try create it with SLAB_NO_MERGE flag so it's really a separate cache. Custom sheaf_capacity might also achieve that effect, but in order to have deterministic results, the flag is a sure way.