From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F05D1501299; Fri, 18 Sep 2026 13:34:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789738472; cv=none; b=U6/OJET5uV3pf8RSMqkvfsr6vUKiNesNylJICH86xlelBGwVKFBbPkIeJiyN7JXM3vcL5RwU72fZqfrLkqG2lBf6WPmgKsKjfy+VBRAcvtBBC6lYzxjkbihAtujuzzeicT9ZdK9GlbLP2UV0hlXc8teOPZ2wLxB4CXLX1MwdYio= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789738472; c=relaxed/simple; bh=R81PMV9/GuF2KWO0tFegcaPSN205KQ6/+Ka0MM24ibs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pbf9JyL55O/KXNlA755Oad6Caqyl/oboqwXpqBqDkpxcy3kPbK2AG2VdtvItjKmmCgREsOoi8cBTIiVf4+zMaierOtxtrt7kfoo8pDSkfw1pSIff7Wj14j1FNtk8J+4ruNbRsUWjIlYrbUa22I7QhKOmjRqUKKfq9cmuvVcEb7A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fb+oI0eB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fb+oI0eB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4F6C1F000FF; Fri, 18 Sep 2026 13:34:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789738470; bh=79tuBX9NtcLOFHYrVaZYnlXt+W9WU4j9rmTOREA3oT4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fb+oI0eBop/lWoz0ykKSm5KiAODDbkMzthqi5lEDcZbXhmawKdxmvKUZlrMSLL5PS WnA4FFrXioEhVBwA/MDsJY3AvT0V/VcNxZGboSI/HOTbXyGdUVwkxas/74LSk0uii/ zVpzGzSl0rfU9bcw3B7zmujjcecVRAWXkcOOBSTTajJjH8Nd/rP6DVvByHPLOHVa0N 3R8JwhT9IA4e9ASMFqsqD1iZ4WW1ME2waj267TBw8inlQpPe/fhUuST5M5u0KGhXGy fctI61XJdFcOmj6F+pJIuEY0soaFsU4jtbhkx4uCEHngq7j1ju+2uNyZgrl37M6S92 CUmJa8kRXhh4g== Message-ID: <82da5375-bae0-4a12-af2c-de82d18769e1@kernel.org> Date: Fri, 18 Sep 2026 15:34:22 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] mm: memcg: don't hand out large folios above memory.high To: Shakeel Butt , Qinyun Tan Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com, roman.gushchin@linux.dev, muchun.song@linux.dev, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, xlpang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, chris@chrisdown.name, kasong@tencent.com, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260915042546.279410-1-qinyuntan@linux.alibaba.com> <20260915042546.279410-2-qinyuntan@linux.alibaba.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 9/18/26 03:26, Shakeel Butt wrote: > On Tue, Sep 15, 2026 at 12:25:46PM +0800, Qinyun Tan wrote: >> memory.high is enforced on return to userspace, and synchronously in > > Over time I feel like this sync throttle for memory.high was a bad decision but > that is an orthogonal discussion. > >> try_charge_memcg() for large overcharges, but only when the charge gfp >> allows blocking. A populate loop - mlock(), MADV_POPULATE_*, any >> GUP-driven population - never returns to userspace, and large folios are >> charged with the THP allocation gfp, which does not allow blocking under >> the default defrag=madvise without MADV_HUGEPAGE, nor under defrag=defer. >> So neither runs: usage grows from memory.high straight up to memory.max >> with no reclaim and no penalty sleep. >> >> mlock(200M) in a cgroup with memory.high=30M and memory.max=140M. Of the >> 110M between high and max, the burst consumed: >> >> 4K pages 3M in 5s, then still throttled >> THP, defrag=always 6M in 5s, then still throttled >> THP, defrag=madvise 110M in 13ms, then OOM killed at 16ms >> THP, defrag=madvise, patched 3M in 5s, then still throttled > > I don't really like polluting non-memcg MM code with memcg internal details. That's the same thought I had when skimming the code. -- Cheers, David