From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (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 C49F0367F59 for ; Tue, 14 Jul 2026 10:53:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784026420; cv=none; b=fgWNJw3+VBLWo3v5c2VEgv/UK9boFqVyjYn126jEPBbonECsWuAohV/3lmQEAAOkLiDh0JvCUj407pnDUmEIFW98kZcHybS4uvL3Dg+ePngTg1DfGkYHA2nhMEWgmOyAECKQwK/25klD6BaflA7Y2wqMV82BZRfE7E2Mmtxueoc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784026420; c=relaxed/simple; bh=yk2woOizaCDdz0CV/MS5s+HZL/VFzG7Il8H5yT1RHgY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F3fBliuoE/w3rvZinvoYZZ8b0VriPtTHDDJIpjguO3PJz+cmi2D84vcyOo3ZZI5uFKM0Cg8ESCVHRxSeNhRDjWPbBobL/tOhw6AUpEyBnuuxvy8bGB4M+FxfRxezo7NsTBl5VQwiq1Eu/KwTvlMrrz/pwnOZHlcxHV5E7WLYOxU= 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=Hr8CWtXv; arc=none smtp.client-ip=95.215.58.177 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="Hr8CWtXv" Message-ID: <3f87f6af-3952-4c16-83fa-9fb77085a285@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784026406; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/LDmA+4RVpARa99Ab+t/25jrDC9AwuxQ6Gu81nLkhgA=; b=Hr8CWtXvQzP2VMAmcJlnKckqOOTkk3iGdGQicebeUy0g3l/oGG59Ca4fqkEdungTTaa/3y baGS7gF9L5q6kyZ1BETnjjODc9EtUAVdVkjDAmOhhK8BYUUSrIPf3OPRXSMx5QH7UdyR7s rr088010fIg34Lex3w5OKYga2sdvUUo= Date: Tue, 14 Jul 2026 18:52:49 +0800 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] fs/super: skip non-memcg-aware nr_cached_objects in memcg slab shrink To: Usama Arif Cc: brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro , linux-mm@kvack.org, hughd@google.com, boris@bur.io, clm@fb.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, cem@kernel.org, linux-xfs@vger.kernel.org, shakeel.butt@linux.dev, hannes@cmpxchg.org, riel@surriel.com, kernel-team@meta.com References: <20260714101740.1270419-1-usama.arif@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20260714101740.1270419-1-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 7/14/26 6:17 PM, Usama Arif wrote: > On Tue, 14 Jul 2026 10:09:26 +0800 Qi Zheng wrote: > >> Hi Usama, >> >> On 7/13/26 11:34 PM, Usama Arif wrote: >>> >>> >>> On 13/07/2026 14:12, Qi Zheng wrote: >>>> Hi Usama, >>>> >>>> On 6/9/26 8:30 PM, Usama Arif wrote: >>>>> The super_block shrinker is registered with SHRINKER_MEMCG_AWARE because its >>>>> dentry and inode LRUs are memcg-aware (via list_lru). But the optional >>>>> ->nr_cached_objects() hooks that the shrinker also drives are not memcg-aware: >>>>> btrfs extent maps and xfs inode reclaim operate on filesystem-global >>>>> state, and shmem's unused-huge shrinker walks a per-superblock shrinklist. >>>>> None of them filter by sc->memcg. >>>> >>>> This makes sense for now, but how should we handle this if these >>>> shrinkers are made memcg-aware in the future? >>>> >>>> I've recently been working on making the shmem huge shrinker >>>> memcg-aware, but noticed my changes broke after rebasing onto the latest >>>> tree, which led me to this patch. >>>> >>>> As for the shmem huge shrinker, I can work around this limitation by >>>> making it a separate shrinker. But this feels more like an overall >>>> design decision, effectively meaning that all nr_cached_objects are >>>> precluded from being memcg-aware. >>>> >>>> Thanks, >>>> Qi >>>> >>> >>> >>> Hi Qi, >>> >>> Thanks for raising this. I think the alternative is what I mentioned in >>> https://lore.kernel.org/all/cfdb8620-ea55-4226-98bf-d006820e6270@linux.dev/ >>> move this down to the fs own callbacks instead of here. Would that >>> be better? >> >> Yes, I think this is a better approach. >> >> Later on, shrinkers that are converted to be memcg-aware can lift this >> restriction themselves. >> >> Thanks, >> Qi > > Thanks Qi, I have sent a patch to push it down to filesystems in [1]. > No functional change inteneded in there. You would have to rebase your > patch on top of that one and remove my code in shmem specifically. Thanks! I will rebase my patch once your patch is merged into linux-next. > > [1] https://lore.kernel.org/all/20260714101454.1202449-1-usama.arif@linux.dev/ > >> >>> >>> Thanks, >>> Usama >> >>