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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1C5DAC433DF for ; Fri, 15 May 2020 21:45:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C962D20756 for ; Fri, 15 May 2020 21:45:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C962D20756 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 572FB8E0003; Fri, 15 May 2020 17:45:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4FAB18E0001; Fri, 15 May 2020 17:45:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 410218E0003; Fri, 15 May 2020 17:45:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0099.hostedemail.com [216.40.44.99]) by kanga.kvack.org (Postfix) with ESMTP id 257068E0001 for ; Fri, 15 May 2020 17:45:32 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D3A2E8248047 for ; Fri, 15 May 2020 21:45:31 +0000 (UTC) X-FDA: 76820285262.22.crack56_1325ef61fd528 X-HE-Tag: crack56_1325ef61fd528 X-Filterd-Recvd-Size: 2758 Received: from gentwo.org (gentwo.org [3.19.106.255]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Fri, 15 May 2020 21:45:31 +0000 (UTC) Received: by gentwo.org (Postfix, from userid 1002) id D25713EBE5; Fri, 15 May 2020 21:45:30 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id D01E83EA5E; Fri, 15 May 2020 21:45:30 +0000 (UTC) Date: Fri, 15 May 2020 21:45:30 +0000 (UTC) From: Christopher Lameter X-X-Sender: cl@www.lameter.com To: Roman Gushchin cc: Andrew Morton , Johannes Weiner , Michal Hocko , linux-mm@kvack.org, kernel-team@fb.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 04/19] mm: slub: implement SLUB version of obj_to_index() In-Reply-To: <20200513005741.GA67541@carbon.dhcp.thefacebook.com> Message-ID: References: <20200423000530.GA63356@carbon.lan> <20200425024625.GA107755@carbon.lan> <20200427164638.GC114719@carbon.DHCP.thefacebook.com> <20200430171558.GA339283@carbon.dhcp.thefacebook.com> <20200504182922.GA20009@carbon.dhcp.thefacebook.com> <20200513005741.GA67541@carbon.dhcp.thefacebook.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 12 May 2020, Roman Gushchin wrote: > > Add it to the metadata at the end of the object. Like the debugging > > information or the pointer for RCU freeing. > > Enabling debugging metadata currently disables the cache merging. > I doubt that it's acceptable to sacrifice the cache merging in order > to embed the memcg pointer? Well then keep the merging even if you have a memcg pointer. The disabling for debugging is only to simplify debugging. You dont have to deal with multiple caches actually using the same storage structures. > Figuring out all these details will likely take several weeks, so the whole > thing will be delayed for one-two major releases (in the best case). Given that > the current implementation saves ~40% of slab memory, I think there is some value > in delivering it as it is. So I wonder if the idea of embedding the pointer > should be considered a blocker, or it can be implemented of top of the proposed > code (given it's not a user-facing api or something like this)? Sorry no idea from my end here.