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[23.128.96.18]) by mx.google.com with ESMTP id bq14si9704906edb.57.2021.09.14.00.17.45; Tue, 14 Sep 2021 00:18:09 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@suse.com header.s=susede1 header.b=bGiWRdKv; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=NONE dis=NONE) header.from=suse.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240653AbhINHPI (ORCPT + 99 others); Tue, 14 Sep 2021 03:15:08 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:39128 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240648AbhINHPH (ORCPT ); Tue, 14 Sep 2021 03:15:07 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id A0D972206C; Tue, 14 Sep 2021 07:13:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1631603629; 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=txwaKhwa12PBU46ZsNcF+1gome0TjZ9CBmHtWzH6uzc=; b=bGiWRdKv8qBHAYo6uY7okxzuUuqOtIaJnnsPyY0NBnjbC/UBbnRIdZrjuEinQDIEeh7Lua pyjg4ZJEJ3A8n65b9stkqC69eFv+zGRtYwaxhXW+yZRELmgGs5oe6WCjHomxHDgTCqmVFR C7erp512iGlIQLgVSZOetkBudr+b8pY= 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 5D439A3B9D; Tue, 14 Sep 2021 07:13:49 +0000 (UTC) Date: Tue, 14 Sep 2021 09:13:48 +0200 From: Michal Hocko To: Shakeel Butt Cc: Vasily Averin , Andrew Morton , Linus Torvalds , LKML , Johannes Weiner , kernel@openvz.org, Cgroups 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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 13-09-21 21:32:25, Shakeel Butt wrote: > On Mon, Sep 13, 2021 at 1:37 AM Michal Hocko wrote: > > > [...] > > > 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? > > > > I don't think there was any regression report or any performance > evaluation. Linus raised the concern on the potential performance > impact. I suggested to backoff for this allocation for now and revisit > again once we have improved the memcg accounting for kernel memory. I am fine with the change, I am just not satisfied with the justification. It is not really clear what the intention is except that Linus wanted it. I have already asked Vasily to provide more explanation. E.g. this part really begs for clarification " 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. " It sounds like a problem, except it is not because? A worst case scenario evaluation would be beneficial for example Thanks! -- Michal Hocko SUSE Labs