From nobody Thu Dec 18 17:43:59 2025 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (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 240D71519AD for ; Thu, 13 Mar 2025 05:48:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741844912; cv=none; b=c/9wR5WJJma4rRZij3ifuS0OQlzDy6OCm9CwuOZaQ8MNxfXFtperCVn5ZV1mDsgMzjCP4C8p8HBI8YJd0zYkbj9jWEjhQsjpSKvP0odGQU1AHpfTjAYcZClBKy/D4WAruu80TpxCqDzS8NxqgGhfxAlvhm69+jtLVRUyrAt7BAg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741844912; c=relaxed/simple; bh=Y81T/0tN+oB0qmAPDllz5PACPLuoxGpwd/0r1MySa+g=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=cOjuJ6EW+7Bl9pvL8MUCTSAMORYGce8MJSfwa46HU77LwyQ50CfXy7OuU4r4lgdIYPIFlvo74lbhSr6QNZeCYLlmWeW9dB9KZTbWyk//Ca9ssmcx8aSZjbAPJHFetFz4iW7z9ODUneSvIRle9I8mq4GtjXtFNB52dJs37Wqu3cE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ISR4blKM; arc=none smtp.client-ip=91.218.175.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ISR4blKM" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1741844898; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=+8crqbD29LSFVEIGtcAdrNxdm4twGCIk3Dwd45ote5E=; b=ISR4blKMWbn1Gw1Y7OO9kCorcO7ZLrAbHXWZBgblKZdMfChIsp8oZ1KwNGXICgyCG38BPX 0Z/0WjlHlK29AG2uiilYcnTyeRlGdojdRdlwDiSLkNCnJfXSemQu69HF3w08qj+UWdqKcv L3W+SoYDjwVURSZnGuHYcx7xUGhNjRY= From: Shakeel Butt To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: [PATCH] memcg: avoid refill_stock for root memcg Date: Wed, 12 Mar 2025 22:48:12 -0700 Message-ID: <20250313054812.2185900-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" We never charge the page counters of root memcg, so there is no need to put root memcg in the memcg stock. At the moment, refill_stock() can be called from try_charge_memcg(), obj_cgroup_uncharge_pages() and mem_cgroup_uncharge_skmem(). The try_charge_memcg() and mem_cgroup_uncharge_skmem() are never called with root memcg, so those are fine. However obj_cgroup_uncharge_pages() can potentially call refill_stock() with root memcg if the objcg object has been reparented over to the root memcg. Let's just avoid refill_stock() from obj_cgroup_uncharge_pages() for root memcg. Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko --- mm/memcontrol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e08ce52caabd..393b73aec6dd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2643,7 +2643,8 @@ static void obj_cgroup_uncharge_pages(struct obj_cgro= up *objcg, =20 mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages); memcg1_account_kmem(memcg, -nr_pages); - refill_stock(memcg, nr_pages); + if (!mem_cgroup_is_root(memcg)) + refill_stock(memcg, nr_pages); =20 css_put(&memcg->css); } --=20 2.47.1