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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 ECC52C4360F for ; Tue, 26 Mar 2019 09:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B977320856 for ; Tue, 26 Mar 2019 09:29:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553592580; bh=j6zoOEW+A+lYDgy9qXFRRwfP9iM4mQcbQuGy0vzHiYY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=0UAcl0AwXWXfztDxnPmKs59mKQa4KDvQA17td5ISef+VtmSGJ9hVLGjwzCunb+88B M6DLnszzC9AD2XLDXO64WHOUy3PYYGKT9S8uEOY0t/hwrGDDlUHNgZxEhEaG35wc4L U+cSMYgNCQyr7VVMuR0CKcV0YZgE5jxfDmZEv0zs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730906AbfCZJ3j (ORCPT ); Tue, 26 Mar 2019 05:29:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:41634 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729334AbfCZJ3i (ORCPT ); Tue, 26 Mar 2019 05:29:38 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 63BC9AC8C; Tue, 26 Mar 2019 09:29:37 +0000 (UTC) Date: Tue, 26 Mar 2019 10:29:36 +0100 From: Michal Hocko To: Baoquan He 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: <20190326092936.GK28406@dhcp22.suse.cz> References: <20190326090227.3059-1-bhe@redhat.com> <20190326090227.3059-3-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326090227.3059-3-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > And also check if section is present earlier. Then don't bother to > allocate usemap and memmap if yes. Moving the check up makes some sense. > Signed-off-by: Baoquan He The patch is not incorrect but I am wondering whether it is really worth it for the current code base. Is it fixing anything real or it is a mere code shuffling to please an eye? > --- > v1->v2: > Do section existence checking earlier to further optimize code. > > mm/sparse.c | 29 +++++++++++------------------ > 1 file changed, 11 insertions(+), 18 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index b2111f996aa6..f4f34d69131e 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -714,20 +714,18 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > ret = sparse_index_init(section_nr, nid); > if (ret < 0 && ret != -EEXIST) > return ret; > - ret = 0; > - memmap = kmalloc_section_memmap(section_nr, nid, altmap); > - if (!memmap) > - return -ENOMEM; > - usemap = __kmalloc_section_usemap(); > - if (!usemap) { > - __kfree_section_memmap(memmap, altmap); > - return -ENOMEM; > - } > > ms = __pfn_to_section(start_pfn); > - if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > - ret = -EEXIST; > - goto out; > + if (ms->section_mem_map & SECTION_MARKED_PRESENT) > + return -EEXIST; > + > + usemap = __kmalloc_section_usemap(); > + if (!usemap) > + return -ENOMEM; > + memmap = kmalloc_section_memmap(section_nr, nid, altmap); > + if (!memmap) { > + kfree(usemap); > + return -ENOMEM; > } > > /* > @@ -739,12 +737,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > section_mark_present(ms); > sparse_init_one_section(ms, section_nr, memmap, usemap); > > -out: > - if (ret < 0) { > - kfree(usemap); > - __kfree_section_memmap(memmap, altmap); > - } > - return ret; > + return 0; > } > > #ifdef CONFIG_MEMORY_HOTREMOVE > -- > 2.17.2 > -- Michal Hocko SUSE Labs