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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 27195C433ED for ; Tue, 6 Apr 2021 11:39:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E98D161394 for ; Tue, 6 Apr 2021 11:39:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243208AbhDFLjW (ORCPT ); Tue, 6 Apr 2021 07:39:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:36424 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242018AbhDFLjJ (ORCPT ); Tue, 6 Apr 2021 07:39:09 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1617709141; 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=4YW0n/W3dPLfWTBXzJ8PJ0h6vYshGydcVQrV/PiOxuQ=; b=RJauROFiVBGV5bknbZbs+Q1gjmqpP0ViVeKyVvWq/asdxT65nzdVEUQDAGBhg52lcZmhWk iJr15TDRFaRtw5fpDqY6aIktpbDmw4H3LaYtzE9iIAY0riB/IuYqNGoNSxvvPy+M+42whi iJH9W8tDZ0EoJ8TEPDTpIymOwI94uRw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id D63B4B154; Tue, 6 Apr 2021 11:39:00 +0000 (UTC) Date: Tue, 6 Apr 2021 13:39:00 +0200 From: Michal Hocko To: Neil Sun Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmscan.c: drop_slab_node with task's memcg Message-ID: References: <1617359934-7812-1-git-send-email-neilsun@yunify.com> <4dba277d-e497-5c34-0e68-fd2283585de2@yunify.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4dba277d-e497-5c34-0e68-fd2283585de2@yunify.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 06-04-21 19:30:22, Neil Sun wrote: > On 2021/4/6 15:21, Michal Hocko wrote: > > > > You are changing semantic of the existing user interface. This knob has > > never been memcg aware and it is supposed to have a global impact. I do > > not think we can simply change that without some users being surprised > > or even breaking them. > > Yes, do you think add new interface to sysfs is a good way? such as > /sys/fs/cgroup/memory/lxc/i-vbe1u8o7/memory.kmem.drop_caches There were other attempts to add a memcg specific alternative to drop_caches. A lack of a strong usecase has been a reason that no such attempt has been merged until now. drop_caches is a problematic interface because it is really coarse and people have learned to (ab)use it to workaround problem rather than fix them properly. What is your usecase? -- Michal Hocko SUSE Labs