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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767130962; bh=vDD527Oy8Bm4F8rGqeZpgVak3XxpV3M7Dw51XP6Clpg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=aKKAzT0AOHTF3wCukkrR5NQA3T+2n0I4882tBgClDuVnnveE8wT0QEV9WJgB3A8pf 5RWyZQUB+eIi6dbF3pM0E9YACVo7rg8vbCn6U0Fcuaac7+PS6a1Aeajnyj5WjX44Zu zcxBuZ67DffcdsMdkOx4mobUwGke5XYjtZzavqdo8JrbNm02sOfICDifAz2G/E5Ln6 yQkBBzc0RNYAjMLKTKOKURwINam7LNU4kO4V5Pkjxly/S6ndVgMPLMB4IWA6w3aa1z dUMzJqH0SVYoKNNt5RgV7BLxvYyNNsMUunkPyjqog5i9OywImEd9UvB2NfGiuKGvLt oGPN/9m8s4gsw== Message-ID: Date: Tue, 30 Dec 2025 22:42:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH next v2 0/2] THP COW support for private executable file mmap To: Matthew Wilcox , Zhang Qilong Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, corbet@lwn.net, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, wangkefeng.wang@huawei.com, sunnanyong@huawei.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, lianux.mm@gmail.com, Nadav Amit References: <20251226100337.4171191-1-zhangqilong3@huawei.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B783F20009 X-Rspamd-Server: rspam03 X-Stat-Signature: ktjingprayiidukeiu8n6kz8hcjh5xb6 X-Rspam-User: X-HE-Tag: 1767130963-860342 X-HE-Meta: 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 bKhXy8v2 K2BhxsIIz4bKUDacCiK2tJmlKbt15zDAUvMm+ 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 12/28/25 04:42, Matthew Wilcox wrote: > On Fri, Dec 26, 2025 at 06:03:35PM +0800, Zhang Qilong wrote: >> The MySQL (Ver 8.0.25) test results on AMD are as follows: >> >> ------------------------------------------------------------------- >> | Exec mmap Rss(kB) | Measured tpmC (NewOrders) | >> -----------------|--------------------|---------------------------| >> base(page COW) | 32868 | 339686 | >> -----------------|--------------------|---------------------------| >> exec THP COW | 43516 | 371324 | >> ------------------------------------------------------------------- >> >> The MySQL using exec THP COW consumes an additional 10648 kB of memory >> but achieves 9.3% performance improvement in the scenario of hotpatch. >> Additionally, another our internal program achieves approximately a 5% >> performance improvement as well. >> >> As result, using exec THP COW will consume additional memory. The >> additional memory consumption may be negligible for the current system. >> It's necessary to balance the memory consumption with the performance >> impact. > > I mean ... you say "negligible", I saay "32% extra". 9% performance > gain is certainly nothing to sneer at (and is consistent with measured > performance gains from using large folios for, eg, kernel compiles). > But wow, that's a lot of extra memory. My feeling is that we shouldn't > add this functionality, but I'd welcome other opinions. Also, I wonder whether there aren't other approaches for such code patching where user space is able to create THPs more effectively? Handling creation of a patched file version etc in user space. E.g., I'd assume that a single "patched" version (with a single THP) for multiple program instances could be beneficial over one patched version per program instance. Which type of code patching does hotpatch perform? -- Cheers David