From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id EA95E6B0033 for ; Wed, 19 Jun 2013 21:44:20 -0400 (EDT) Date: Thu, 20 Jun 2013 10:44:40 +0900 From: Joonsoo Kim Subject: Re: [PATCH] slub: do not put a slab to cpu partial list when cpu_partial is 0 Message-ID: <20130620014439.GA13026@lge.com> References: <1371623635-26575-1-git-send-email-iamjoonsoo.kim@lge.com> <51c1652d.246e320a.4057.ffffed4fSMTPIN_ADDED_BROKEN@mx.google.com> <20130619085250.GC12231@lge.com> <51c24c29.425c320a.433e.ffff9d8fSMTPIN_ADDED_BROKEN@mx.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51c24c29.425c320a.433e.ffff9d8fSMTPIN_ADDED_BROKEN@mx.google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Pekka Enberg , Christoph Lameter , Matt Mackall , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Jun 20, 2013 at 08:26:03AM +0800, Wanpeng Li wrote: > On Wed, Jun 19, 2013 at 05:52:50PM +0900, Joonsoo Kim wrote: > >On Wed, Jun 19, 2013 at 04:00:32PM +0800, Wanpeng Li wrote: > >> On Wed, Jun 19, 2013 at 03:33:55PM +0900, Joonsoo Kim wrote: > >> >In free path, we don't check number of cpu_partial, so one slab can > >> >be linked in cpu partial list even if cpu_partial is 0. To prevent this, > >> >we should check number of cpu_partial in put_cpu_partial(). > >> > > >> > >> How about skip get_partial entirely? put_cpu_partial is called > >> in two paths, one is during refill cpu partial lists in alloc > >> slow path, the other is in free slow path. And cpu_partial is 0 > >> just in debug mode. > >> > >> - alloc slow path, there is unnecessary to call get_partial > >> since cpu partial lists won't be used in debug mode. > >> - free slow patch, new.inuse won't be true in debug mode > >> which lead to put_cpu_partial won't be called. > >> > > > >In debug mode, put_cpu_partial() can't be called already on both path. > >But, if we assign 0 to cpu_partial via sysfs, put_cpu_partial() will be called > >on free slow path. On alloc slow path, it can't be called, because following > >test in get_partial_node() is always failed. > > > >available > s->cpu_partial / 2 > > Is it always true? We can freeze slab from partial list, and > s->cpu_partial is 0. Do you mean node partial list? At first, acquire_slab() is called for a cpu slab(not cpu partial list) in get_partial_node(), and then, check above test. In this time, available is always higher than 0, so, if we assign 0 to s->cpu_partial, we break the loop and we don't try to get a slab for cpu partial list. Thanks. > > Regards, > Wanpeng Li > > > > >Thanks. > > > >> Regards, > >> Wanpeng Li > >> > >> >Signed-off-by: Joonsoo Kim > >> > > >> >diff --git a/mm/slub.c b/mm/slub.c > >> >index 57707f0..7033b4f 100644 > >> >--- a/mm/slub.c > >> >+++ b/mm/slub.c > >> >@@ -1955,6 +1955,9 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain) > >> > int pages; > >> > int pobjects; > >> > > >> >+ if (!s->cpu_partial) > >> >+ return; > >> >+ > >> > do { > >> > pages = 0; > >> > pobjects = 0; > >> >-- > >> >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 > >> > >> -- > >> 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 -- 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