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Thu, 14 May 2026 19:06:10 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 9060F402AB; Thu, 14 May 2026 19:13:46 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 14 May 2026 19:13:45 +0800 Message-ID: Date: Thu, 14 May 2026 19:13:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/damon/vaddr: attempt per-vma lock during page table walk To: SeongJae Park CC: Andrew Morton , , , References: <20260514020059.149541-1-sj@kernel.org> Content-Language: en-US From: Kefeng Wang In-Reply-To: <20260514020059.149541-1-sj@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf100008.china.huawei.com (7.185.36.138) X-Stat-Signature: nysr5ifygcioxqjmnfr3z438sf5gjkko X-Rspamd-Queue-Id: 566E510000B X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1778757231-4959 X-HE-Meta: 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 iA/i2yxx s5cqO6OhOV4nc/SrXeRHVmVzL3r9y0BNcL7Qv/5gvS2FHApvHaCEj9naaun56nRWA2FBeYe/S7JFaA0Lz3B+UHZzSo5X7LnXxn7Y15Ik4UDhqc2OEzPffX5F+N2qvXBwtN5X2leb605nVBY8yZUyGGL+p9PxpcZ6ORAaXHB5zUnrEFLyHZZKcqij5ihPa08drKAr79YkjrhhqtR3pISa/QEq2UVAP1vwCYDtLpCE2iYd+gR2Udu3Rlu8Zj2tRBbzW73fDeehhaJlEjgNwf6fpxEDB2QzfEc46AZWVm0awiMRq6GrjSZhEUJP2baTQulXUhkRnKDJP+yC1wQMeT6NBV+MPnkewA4fxu1AVctHFMF8WuKg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/14/2026 10:00 AM, SeongJae Park wrote: > On Tue, 12 May 2026 23:15:23 +0800 Kefeng Wang wrote: > >> Currently, DAMON virtual address operations use mmap_read_lock >> during page table walks, which can cause unnecessary contention >> under high concurrency. >> >> Introduce damon_va_walk_page_range() to first attempt acquiring a >> per-vma lock. If the VMA is found and the range is fully contained >> within it, the page table walk proceeds with the per-vma lock >> instead of mmap_read_lock. >> >> This optimization is particularly effective for damon_va_young() >> and damon_va_mkold(), which are frequently called and typically >> operate within a single VMA. > > Maybe this is not only making DAMON faster, but avoid DAMON blocking others. > Yes, this is exactly what per-vma is for. > And because we don't have performance measurements, how about making this > sentence less assertive? E.g., "This optimization is particularly expected to > be effective for ..." Fine to me. > > I guess Andrew could make the adjustment when he picks this into mm.git. If > not I will repost this with the trivial change if you don't mind. > >> Sure >> Signed-off-by: Kefeng Wang > > Reviewed-by: SeongJae Park > Thanks >> --- >> v2: avoid handling VMAs with the VM_PFNMAP for per-vma path, found by >> Sashiko review. > > This patch helped Sashiko finding [1] yet another DAMON bug (impact is minor > imho). The bug is orthogonal to this patch so there is no blocker for this > patch. > >> v1: https://lore.kernel.org/linux-mm/20260511132546.1973270-1-wangkefeng.wang@huawei.com/ > > [1] https://lore.kernel.org/20260514015053.149396-1-sj@kernel.org > > > Thanks, > SJ > > [...] >