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bh=7wPcm/Xetdm2u1ZsAsdit/mG1QKFMGsSy/lP1k1Fymo=; b=MT89gbulWDwC1GE0zPuOvswRk3u8jgt2y4BUnIna5K3drboum+6auwnO4MbnWntc94hskn MaKc8WYFS/fsJBas/T6Rx/sePVAhsjIcK+M1BAZ0wtNltRtr4s+q23SGD1uIQXoNiGDrig a8q8Z6wsiEak6lQgTjNfP6jdkZttIxA= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=R86JUREA; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf12.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id BEFB4600BB; Tue, 30 Jun 2026 05:38:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2506F1F000E9; Tue, 30 Jun 2026 05:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782797928; bh=7wPcm/Xetdm2u1ZsAsdit/mG1QKFMGsSy/lP1k1Fymo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=R86JUREAVLX4ULzfoTYjiYDdOZfMIayeZs90it0vFa8kQ64Ls1ie0TAwLP5123vs5 g5KD2E6E0wFmYPJtTnTOyxnxHreqJ27IsO+hMszlJeDAub0hlgwa+XlwwpZdhSmt53 b7x28y/AtxeJcNKfWqeNaANQEuaPFV6o4UcdLxzENTDDklldkr17moKQlRn3dChK2L F9oIJ/pg1wmOxRdmoDuajZiM/ZobAH01ip04NmGhPqS8A/47CCBKyRGhYamu4hbLV1 Dffj+dDIJCjY0SqHA8fllTtPrfen7PiIkCqW/+WEZmPzykGGPKdTYWCIGcOahHhWJm ym3B6eh7F3GxA== Message-ID: <0c386af6-353c-4f76-9f28-bd1a77dababe@kernel.org> Date: Tue, 30 Jun 2026 07:38:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] mm: avoid unnecessary lru drain for wp_can_reuse_anon_folio() To: Barry Song Cc: Shakeel Butt , akpm@linux-foundation.org, linux-mm@kvack.org, baoquan.he@linux.dev, chrisl@kernel.org, jp.kobryn@linux.dev, kasong@tencent.com, liam@infradead.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, nphamcs@gmail.com, rppt@kernel.org, shikemeng@huaweicloud.com, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, youngjun.park@lge.com References: <20260623231635.43086-1-baohua@kernel.org> <20260623231635.43086-2-baohua@kernel.org> <3903def5-e823-4fe3-9784-b6bd63470516@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 65DFF40006 X-Rspam-User: X-Stat-Signature: dxgp1txwpifdbj5bfyo88ncr45m3jco8 X-HE-Tag: 1782797929-413639 X-HE-Meta: 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 6tbbPkoo xW0yQf+Na8fBmudnzpgRddeqNQRdxEy8Y8NVO/JDOsxPlGZ1/l5sILMgIFNvF1CsWj3veNJdT/owcA/XP8hAykvCmgBcRpqj5WOBqIb6kvpBqr3I+CmQPhOp/ryM0R0W22lYNUQWH9TIk2NFYFRFfrsUah0/x+DMh8KwuVQ99w4ode7hzN83I5iwuz2AWXJv6py5xONjnyWcZnCzOAaZ/KDPHvMHfprJcdoFRF7rBXWN4gSGGo8Ns67lwrgNKA49J0yqweQ5x2JOxv3nn4+89ai8aMXDH4quns+jMoWfooSc2PkIqRUxemYr9SG0pXbNepLdPgBd03kEpqg6VM0aSh6gQR3tmfx6N5uwglFBdS5QCnRIf8JPu6/9Myk2FDc/QeLA8zyYaM/ZMCLQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/30/26 01:16, Barry Song wrote: > On Mon, Jun 29, 2026 at 3:52 PM David Hildenbrand (Arm) > wrote: > [...] >> >> So yeah, if Nadav's reproducer works even without the drain (which I assume), we >> could indeed think about just removing this optimization here. > > Yet I think the problem is resolved with the exclusive flag. > Right now, we can still have cases where "exclusive" cannot > address it, such as: > > #include > > int main(int argc, char *argv[]) > { > int i; > #define SIZE 30*1024*1024 > while(1) { > volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > volatile int q; > > for (int i = 0; i < SIZE/sizeof(int); i++) > p[i] = i; > madvise((void *)p, SIZE, MADV_PAGEOUT); > if (!fork()) > _exit(0); > for (int i = 0; i < SIZE/sizeof(int); i++) > q = p[i]; > for (int i = 0; i < SIZE/sizeof(int); i++) > p[i] = i; > munmap(p, SIZE); > } > return 0; > } > > I assume this is less frequent and less of a concern? It's unlikely to matter in practice I guess. -- Cheers, David