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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 AC819C43381 for ; Tue, 26 Mar 2019 14:18:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67E182075D for ; Tue, 26 Mar 2019 14:18:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731776AbfCZOSI (ORCPT ); Tue, 26 Mar 2019 10:18:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58184 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726266AbfCZOSI (ORCPT ); Tue, 26 Mar 2019 10:18:08 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A321185545; Tue, 26 Mar 2019 14:18:07 +0000 (UTC) Received: from localhost (ovpn-12-21.pek2.redhat.com [10.72.12.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2EC4B1001E81; Tue, 26 Mar 2019 14:18:05 +0000 (UTC) Date: Tue, 26 Mar 2019 22:18:03 +0800 From: Baoquan He To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, rppt@linux.ibm.com, osalvador@suse.de, willy@infradead.org, william.kucharski@oracle.com Subject: Re: [PATCH v2 2/4] mm/sparse: Optimize sparse_add_one_section() Message-ID: <20190326141803.GX3659@MiWiFi-R3L-srv> References: <20190326090227.3059-1-bhe@redhat.com> <20190326090227.3059-3-bhe@redhat.com> <20190326092936.GK28406@dhcp22.suse.cz> <20190326100817.GV3659@MiWiFi-R3L-srv> <20190326101710.GN28406@dhcp22.suse.cz> <20190326134522.GB21943@MiWiFi-R3L-srv> <20190326140348.GQ28406@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326140348.GQ28406@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Tue, 26 Mar 2019 14:18:07 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/26/19 at 03:03pm, Michal Hocko wrote: > On Tue 26-03-19 21:45:22, Baoquan He wrote: > > On 03/26/19 at 11:17am, Michal Hocko wrote: > > > On Tue 26-03-19 18:08:17, Baoquan He wrote: > > > > On 03/26/19 at 10:29am, Michal Hocko wrote: > > > > > On Tue 26-03-19 17:02:25, Baoquan He wrote: > > > > > > Reorder the allocation of usemap and memmap since usemap allocation > > > > > > is much simpler and easier. Otherwise hard work is done to make > > > > > > memmap ready, then have to rollback just because of usemap allocation > > > > > > failure. > > > > > > > > > > Is this really worth it? I can see that !VMEMMAP is doing memmap size > > > > > allocation which would be 2MB aka costly allocation but we do not do > > > > > __GFP_RETRY_MAYFAIL so the allocator backs off early. > > > > > > > > In !VMEMMAP case, it truly does simple allocation directly. surely > > > > usemap which size is 32 is smaller. So it doesn't matter that much who's > > > > ahead or who's behind. However, this benefit a little in VMEMMAP case. > > > > > > How does it help there? The failure should be even much less probable > > > there because we simply fall back to a small 4kB pages and those > > > essentially never fail. > > > > OK, I am fine to drop it. Or only put the section existence checking > > earlier to avoid unnecessary usemap/memmap allocation? > > DO you have any data on how often that happens? Should basically never > happening, right? Oh, you think about it in this aspect. Yes, it rarely happens. Always allocating firstly can increase efficiency. Then I will just drop it.