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 X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEAB5C433EF for ; Mon, 13 Sep 2021 08:37:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C308A60F46 for ; Mon, 13 Sep 2021 08:37:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234575AbhIMIiu (ORCPT ); Mon, 13 Sep 2021 04:38:50 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:47108 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238029AbhIMIiY (ORCPT ); Mon, 13 Sep 2021 04:38:24 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id BD6661FFAA; Mon, 13 Sep 2021 08:37:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1631522227; 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=UKSu3yTv+TX0tXlcSUO37sd0/aOo8J1xv19A7FZ7+Ig=; b=ZMT+0AgcgH+hRJCL2ffTYbCzZn/BEVzdgyChbAJf+WYp+HMrwdkFDOqIR/wbhIEDQaJ3dS VDxQV9ERlW08pJz64yBgAYXVsCo2ljnNryj8wTbreIMQM32Ehb0ZAbbPkmtK1oYCdaCbCq 22d+IBxpaQQO5LXBt5yF+0v5WHrDATY= 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 8874EA3B81; Mon, 13 Sep 2021 08:37:07 +0000 (UTC) Date: Mon, 13 Sep 2021 10:37:02 +0200 From: Michal Hocko To: Vasily Averin Cc: Andrew Morton , Linus Torvalds , Shakeel Butt , linux-kernel@vger.kernel.org, Johannes Weiner , kernel@openvz.org, cgroups@vger.kernel.org Subject: Re: [PATCH] ipc: remove memcg accounting for sops objects in do_semtimedop() Message-ID: References: <90e254df-0dfe-f080-011e-b7c53ee7fd20@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <90e254df-0dfe-f080-011e-b7c53ee7fd20@virtuozzo.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 11-09-21 10:40:08, Vasily Averin wrote: > Linus proposes to revert an accounting for sops objects in > do_semtimedop() because it's really just a temporary buffer > for a single semtimedop() system call. > > This object can consume up to 2 pages, syscall is sleeping one, > size and duration can be controlled by user, and this allocation > can be repeated by many thread at the same time. Is there any upper bound or is it just bounded by the number of tasks/threads (that can be controlled by pid controller at least)? > However Shakeel Butt pointed that there are much more popular objects > with the same life time and similar memory consumption, the accounting > of which was decided to be rejected for performance reasons. Is there any measurable performance impact in this particular case? > In addition, any usual task consumes much more accounted memory, > so 2 pages of this temporal buffer can be safely ignored. > > Link: https://patchwork.kernel.org/project/linux-fsdevel/patch/20171005222144.123797-1-shakeelb@google.com/ > > Fixes: 18319498fdd4 ("memcg: enable accounting of ipc resources") > Signed-off-by: Vasily Averin > --- > ipc/sem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/ipc/sem.c b/ipc/sem.c > index f833238df1ce..6693daf4fe11 100644 > --- a/ipc/sem.c > +++ b/ipc/sem.c > @@ -2238,7 +2238,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops, > return -EINVAL; > > if (nsops > SEMOPM_FAST) { > - sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL_ACCOUNT); > + sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL); > if (sops == NULL) > return -ENOMEM; > } > -- > 2.25.1 -- Michal Hocko SUSE Labs