From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx195.postini.com [74.125.245.195]) by kanga.kvack.org (Postfix) with SMTP id 7BB106B0135 for ; Tue, 26 Jun 2012 02:08:47 -0400 (EDT) Received: from /spool/local by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 26 Jun 2012 00:08:45 -0600 Received: from d03relay05.boulder.ibm.com (d03relay05.boulder.ibm.com [9.17.195.107]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 2B13D19D804F for ; Tue, 26 Jun 2012 06:07:50 +0000 (WET) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay05.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q5Q67r59261606 for ; Tue, 26 Jun 2012 00:07:53 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q5Q67qYc017763 for ; Tue, 26 Jun 2012 00:07:53 -0600 Date: Tue, 26 Jun 2012 14:07:35 +0800 From: Gavin Shan Subject: Re: [PATCH 2/5] mm/sparse: optimize sparse_index_alloc Message-ID: <20120626060735.GA9483@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120625153035.GB19810@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 >> 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 :-) 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 > -- 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