From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE19E39936B; Tue, 12 May 2026 09:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778578105; cv=none; b=qReU7QDvchescwZMowU+dx++/ylTfkDeC/Q57mu418L4kSFbk78jl4yE9W/GEKPIhjPTpsjEhnA8wuStkHSj/gyczxurm0M9ILZVXTRgYqH8MVnDz72FdvqCnJyUT/XP+KmMpLaxBoxEKPEAPaIsswdFnMnahkOTho1vDLbHLyc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778578105; c=relaxed/simple; bh=0E5IxBKbz4u4hg2v2fd+BVV/esRQq2aK57wXBGGDo7g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gxlPL28PaBxhVZaj0x8emMafn+T4L4GM2p2WBC0xkWJ1JEl6quDm3xVOIVNiGkXcrMTr1AW0Lay9puiWpVTO/SmbK8vlTpzuX7epJ3E3IpXh3dwcBKS3/n8co5F5x52TUbPRugU1X/IwChfwfyjuAVDUBPq+B2IPbXgnTRQGRok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Qpi4KKNX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Qpi4KKNX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28E7CC2BCB0; Tue, 12 May 2026 09:28:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778578105; bh=0E5IxBKbz4u4hg2v2fd+BVV/esRQq2aK57wXBGGDo7g=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Qpi4KKNXGcN58BJXlD58i5Xlxu6vbfqPhXibd9sFp/0BeN1+aY+vOK/C7xbEORQaN FnguCTSycv3dR2Edh4bCbAsdRtGNZfITNUQbrjSg+xBlrbyRwP4HxtX7kMqFG7hnk2 ZCGA8oeP6h4wsfNS7+r/sueekLbwjyiaUMw1Ku6Ko258CF0sH8Hcc54/lMdR41A6e/ qNhiRD0kinDKblm8pQ50/n6nDC+G/dQ7Zd6oK7PEnyWgADOBXlcnV+oI8R7WumXMrY tAcsQI9wexgSOWBDj+Xqo2q7xtfRNEkLmUke5JHFhIdB38YFbGUv5S2axnYAlcXoLV oI5JXgBRH2brg== Message-ID: Date: Tue, 12 May 2026 11:28:20 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] use vma locks for proc/pid/{smaps|numa_maps} reads To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, willy@infradead.org, jannh@google.com, paulmck@kernel.org, pfalcato@suse.de, shuah@kernel.org, hsukrut3@gmail.com, richard.weiyang@gmail.com, reddybalavignesh9979@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260426062718.1238437-1-surenb@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/26/26 08:27, Suren Baghdasaryan wrote: > Use per-vma locks when reading /proc/pid/smaps and /proc/pid/numa_maps > similar to /proc/pid/maps to reduce contention on central mmap_lock. One > major difference between maps and smaps/numa_maps reading is that the > latter executes page table walk which can't be done under RCU due to a > possibility of sleeping. Therefore we drop RCU read lock before this walk > while keeping the VMA locked. After the walk we retake RCU read lock, > reset VMA iterator and proceed with the next VMA. With many small VMAs, is that overhead noticable? -- Cheers, David