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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 691A6C433EF for ; Thu, 14 Oct 2021 15:13:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D0EF60F4A for ; Thu, 14 Oct 2021 15:13:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232480AbhJNPPr (ORCPT ); Thu, 14 Oct 2021 11:15:47 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:55968 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231148AbhJNPPp (ORCPT ); Thu, 14 Oct 2021 11:15:45 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 7E4441FD39; Thu, 14 Oct 2021 15:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1634224419; 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=QE4+A40zXiKCiQ946QCo1/U24aTkHA32OG4HCqemGgQ=; b=LfxkknrhXNsBI23uUnynPj0T/3sYGaQU2Lce7KpdjjlqDHbi0zRgYT482Jr3NdviS1kNEp 1xCNxU7X/Ju96xFEeWLSc7xxqT0GcZfsgXXmYRMUlYP4fxM1AGKMwwqRi27BlG9r0tKFoO 1DHxQDZ7OE11EN1lz+znIwQp4FnTWVE= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 59965A3B81; Thu, 14 Oct 2021 15:13:39 +0000 (UTC) Date: Thu, 14 Oct 2021 17:13:39 +0200 From: Michal Hocko To: Shakeel Butt Cc: Johannes Weiner , Mel Gorman , Uladzislau Rezki , Vasily Averin , Roman Gushchin , Andrew Morton , Cgroups , Linux MM , LKML Subject: Re: [PATCH] memcg: page_alloc: skip bulk allocator for __GFP_ACCOUNT Message-ID: References: <20211013194338.1804247-1-shakeelb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 14-10-21 08:01:16, Shakeel Butt wrote: > On Thu, Oct 14, 2021 at 12:16 AM Michal Hocko wrote: > > > > On Wed 13-10-21 12:43:38, Shakeel Butt wrote: > > [...] > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 668edb16446a..b3acad4615d3 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -5215,6 +5215,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, > > > unsigned int alloc_flags = ALLOC_WMARK_LOW; > > > int nr_populated = 0, nr_account = 0; > > > > > > + /* Bulk allocator does not support memcg accounting. */ > > > + if (unlikely(gfp & __GFP_ACCOUNT)) > > > + goto out; > > > > Did you mean goto failed here? This would break some which do not > > have any fallback. E.g. xfs_buf_alloc_pages but likely more. > > > > Sorry I could have been more specific when talking about bypassing the > > bulk allocator. It is quite confusing because the bulk allocator > > interface consists of the bulk allocator and the fallback to the normal > > page allocator. > > > > I did consider 'goto failed' here but for that I have to move > __GFP_ACCOUNT check after the "Already populated array" check in the > function. Basically what's the point of doing other operations > (incrementing nr_populated) if we are gonna skip bulk anyways. I have to say I do not follow why that is a problem. > Regarding xfs_buf_alloc_pages(), it is not using __GFP_ACCOUNT and > vmalloc() is the only __GFP_ACCOUNT user at this point. So, not an > issue for now but I suppose it is better to be future-proof and do the > 'goto failed'. Why do we want to have that silent trap? -- Michal Hocko SUSE Labs