From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81F19E7543A for ; Tue, 3 Oct 2023 09:17:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239584AbjJCJRz (ORCPT ); Tue, 3 Oct 2023 05:17:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231533AbjJCJRv (ORCPT ); Tue, 3 Oct 2023 05:17:51 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66A27AF; Tue, 3 Oct 2023 02:17:47 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 050512189A; Tue, 3 Oct 2023 09:17:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1696324666; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tHMY/QK7iViujm+75eY0KL1YTgmg3x9ujdg7FPt3TI8=; b=OZcPJ8KLJgaqqBIZ9hziftqLWT/5Y6IhTybSpPiZOUyssGqjfwWFz54YyMW7FaL+dKBlJv VBm4OntUrg4/OGf1j101r6hnTUdboh4qHxao0EolR+hTJQM37P+atlbiurMHIfmTYOi+DN AN8l1z9bhEjLJ0sceYNh7Mow9zBzoVA= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id E8FCF139F9; Tue, 3 Oct 2023 09:17:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id ZdZFODncG2U5SAAAMHmgww (envelope-from ); Tue, 03 Oct 2023 09:17:45 +0000 Date: Tue, 3 Oct 2023 11:17:45 +0200 From: Michal Hocko To: Johannes Weiner Cc: Nhat Pham , akpm@linux-foundation.org, riel@surriel.com, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, tj@kernel.org, lizefan.x@bytedance.com, shuah@kernel.org, mike.kravetz@oracle.com, yosryahmed@google.com, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH v2 1/2] hugetlb: memcg: account hugetlb-backed memory in memory controller Message-ID: References: <20230928005723.1709119-1-nphamcs@gmail.com> <20230928005723.1709119-2-nphamcs@gmail.com> <20231002145026.GB4414@cmpxchg.org> <20231002152555.GA5054@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231002152555.GA5054@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 02-10-23 11:25:55, Johannes Weiner wrote: > On Mon, Oct 02, 2023 at 05:08:34PM +0200, Michal Hocko wrote: > > On Mon 02-10-23 10:50:26, Johannes Weiner wrote: > > > On Mon, Oct 02, 2023 at 03:43:19PM +0200, Michal Hocko wrote: > > > > On Wed 27-09-23 17:57:22, Nhat Pham wrote: > > [...] > > > > - memcg limit reclaim doesn't assist hugetlb pages allocation when > > > > hugetlb overcommit is configured (i.e. pages are not consumed from the > > > > pool) which means that the page allocation might disrupt workloads > > > > from other memcgs. > > > > - failure to charge a hugetlb page results in SIGBUS rather > > > > than memcg oom killer. That could be the case even if the > > > > hugetlb pool still has pages available and there is > > > > reclaimable memory in the memcg. > > > > > > Are these actually true? AFAICS, regardless of whether the page comes > > > from the pool or the buddy allocator, the memcg code will go through > > > the regular charge path, attempt reclaim, and OOM if that fails. > > > > OK, I should have been more explicit. Let me expand. Charges are > > accounted only _after_ the actual allocation is done. So the actual > > allocation is not constrained by the memcg context. It might reclaim > > from the memcg at that time but the disruption could have already > > happened. Not really any different from regular memory allocation > > attempt but much more visible with GB pages and one could reasonably > > expect that memcg should stop such a GB allocation if the local reclaim > > would be hopeless to free up enough from its own consumption. > > > > Makes more sense? > > Yes, that makes sense. > > This should be fairly easy to address by having hugetlb do the split > transaction that charge_memcg() does in one go, similar to what we do > for the hugetlb controller as well. IOW, > > alloc_hugetlb_folio() > { > if (mem_cgroup_hugetlb_try_charge()) > return ERR_PTR(-ENOMEM); > > folio = dequeue(); > if (!folio) { > folio = alloc_buddy(); > if (!folio) > goto uncharge; > } > > mem_cgroup_hugetlb_commit_charge(); > } yes, this makes sense. I still suspect we will need a better charge reclaim tuning for GB pages as those are just too huge and a simple MAX_RECLAIM_RETRIES * GB worth of reclaim targets might be just overly aggressive. -- Michal Hocko SUSE Labs