From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx137.postini.com [74.125.245.137]) by kanga.kvack.org (Postfix) with SMTP id 4A4956B0144 for ; Tue, 26 Jun 2012 03:15:04 -0400 (EDT) Received: from /spool/local by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 26 Jun 2012 01:15:03 -0600 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 4276819D804A for ; Tue, 26 Jun 2012 07:14:37 +0000 (WET) Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q5Q7E9lI174830 for ; Tue, 26 Jun 2012 01:14:24 -0600 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q5Q7DrU2017930 for ; Tue, 26 Jun 2012 01:13:53 -0600 Date: Tue, 26 Jun 2012 15:13:50 +0800 From: Gavin Shan Subject: Re: [PATCH 2/5] mm/sparse: optimize sparse_index_alloc Message-ID: <20120626071350.GA22907@shangw> Reply-To: Gavin Shan References: <1340466776-4976-1-git-send-email-shangw@linux.vnet.ibm.com> <1340466776-4976-2-git-send-email-shangw@linux.vnet.ibm.com> <20120625153035.GB19810@tiehlicka.suse.cz> <20120626060735.GA9483@shangw> <20120626070421.GA6713@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120626070421.GA6713@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Gavin Shan , linux-mm@kvack.org, rientjes@google.com, hannes@cmpxchg.org, akpm@linux-foundation.org On Tue, Jun 26, 2012 at 09:04:21AM +0200, Michal Hocko wrote: >On Tue 26-06-12 14:07:35, Gavin Shan wrote: >> >> With CONFIG_SPARSEMEM_EXTREME, the two level of memory section >> >> descriptors are allocated from slab or bootmem. When allocating >> >> from slab, let slab allocator to clear the memory chunk. However, >> >> the memory chunk from bootmem allocator, we have to clear that >> >> explicitly. >> > >> >I am sorry but I do not see how this optimize the current code. What is >> >the difference between slab doing memset and doing it explicitly for all >> >cases? >> > >> >> Yeah, I do agree it won't do much optimization here. However, I'm wandering >> if I can remove the whole peice of code doing memset(setion, 0, array_size) >> since it seems that alloc_bootmem_node() also clears the allocated memory >> chunk :-) > >Yes, alloc_bootem_node clears the memory (strange, I thought it doesn't >do that), so the memset is really not necessary after s/kmalloc/kzalloc/. > Thanks for the confirm, Michal. Let me remove it in next revision :-) Thanks, Gavin >> >> Please correct me if I'm wrong about alloc_bootmem_node() :-) >> >> Thanks, >> Gavin >> >> >> >> >> Signed-off-by: Gavin Shan >> >> --- >> >> mm/sparse.c | 12 ++++++------ >> >> 1 file changed, 6 insertions(+), 6 deletions(-) >> >> >> >> diff --git a/mm/sparse.c b/mm/sparse.c >> >> index afd0998..ce50c8b 100644 >> >> --- a/mm/sparse.c >> >> +++ b/mm/sparse.c >> >> @@ -74,14 +74,14 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid) >> >> >> >> if (slab_is_available()) { >> >> if (node_state(nid, N_HIGH_MEMORY)) >> >> - section = kmalloc_node(array_size, GFP_KERNEL, nid); >> >> + section = kzalloc_node(array_size, GFP_KERNEL, nid); >> >> else >> >> - section = kmalloc(array_size, GFP_KERNEL); >> >> - } else >> >> + section = kzalloc(array_size, GFP_KERNEL); >> >> + } else { >> >> section = alloc_bootmem_node(NODE_DATA(nid), array_size); >> >> - >> >> - if (section) >> >> - memset(section, 0, array_size); >> >> + if (section) >> >> + memset(section, 0, array_size); >> >> + } >> >> >> >> return section; >> >> } >> >> -- >> >> 1.7.9.5 >> >> >> >> -- >> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> >> the body to majordomo@kvack.org. For more info on Linux MM, >> >> see: http://www.linux-mm.org/ . >> >> Don't email: email@kvack.org >> > >> >-- >> >Michal Hocko >> >SUSE Labs >> >SUSE LINUX s.r.o. >> >Lihovarska 1060/12 >> >190 00 Praha 9 >> >Czech Republic >> > >> >-- >> >To unsubscribe, send a message with 'unsubscribe linux-mm' in >> >the body to majordomo@kvack.org. For more info on Linux MM, >> >see: http://www.linux-mm.org/ . >> >Don't email: email@kvack.org >> > >> > >-- >Michal Hocko >SUSE Labs >SUSE LINUX s.r.o. >Lihovarska 1060/12 >190 00 Praha 9 >Czech Republic > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org