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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 26 Mar 2019 13:57:11 -0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2QDvAUu53018786 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Mar 2019 13:57:10 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 22B614204F; Tue, 26 Mar 2019 13:57:10 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3B08142042; Tue, 26 Mar 2019 13:57:09 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.207.52]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 26 Mar 2019 13:57:09 +0000 (GMT) Date: Tue, 26 Mar 2019 15:57:07 +0200 From: Mike Rapoport To: Baoquan He Cc: Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, osalvador@suse.de, willy@infradead.org, william.kucharski@oracle.com Subject: Re: [PATCH v2 2/4] mm/sparse: Optimize sparse_add_one_section() 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190326134522.GB21943@MiWiFi-R3L-srv> User-Agent: Mutt/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19032613-0028-0000-0000-000003587834 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032613-0029-0000-0000-00002417302C Message-Id: <20190326135706.GB23024@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-26_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903260098 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, Mar 26, 2019 at 09:45:22PM +0800, 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? > > > From 7594b86ebf5d6fcc8146eca8fc5625f1961a15b1 Mon Sep 17 00:00:00 2001 > From: Baoquan He > Date: Tue, 26 Mar 2019 18:48:39 +0800 > Subject: [PATCH] mm/sparse: Check section's existence earlier in > sparse_add_one_section() > > No need to allocate usemap and memmap if section has been present. > And can clean up the handling on failure. > > Signed-off-by: Baoquan He > --- > mm/sparse.c | 21 ++++++++------------- > 1 file changed, 8 insertions(+), 13 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 363f9d31b511..f564b531e0f7 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -714,7 +714,13 @@ 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; > + > + ms = __pfn_to_section(start_pfn); > + if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > + ret = -EEXIST; > + goto out; return -EEXIST; ? > + } > + > memmap = kmalloc_section_memmap(section_nr, nid, altmap); > if (!memmap) > return -ENOMEM; > @@ -724,12 +730,6 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > return -ENOMEM; > } > > - ms = __pfn_to_section(start_pfn); > - if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > - ret = -EEXIST; > - goto out; > - } > - > /* > * Poison uninitialized struct pages in order to catch invalid flags > * combinations. > @@ -739,12 +739,7 @@ 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 > -- Sincerely yours, Mike.