From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: Re: [PATCH 6/6] mm: page_alloc: Reduce cost of the fair zone allocation policy Date: Mon, 11 Aug 2014 13:12:42 +0100 Message-ID: <20140811121241.GD7970@suse.de> References: <1404893588-21371-1-git-send-email-mgorman@suse.de> <1404893588-21371-7-git-send-email-mgorman@suse.de> <53E4EC53.1050904@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Cc: Andrew Morton , Linux Kernel , Linux-MM , Linux-FSDevel , Johannes Weiner To: Vlastimil Babka Return-path: Content-Disposition: inline In-Reply-To: <53E4EC53.1050904@suse.cz> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Aug 08, 2014 at 05:27:15PM +0200, Vlastimil Babka wrote: > On 07/09/2014 10:13 AM, Mel Gorman wrote: > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1604,6 +1604,9 @@ again: > > } > > > > __mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order)); > > This can underflow zero, right? > Yes, because of per-cpu accounting drift. > > + if (zone_page_state(zone, NR_ALLOC_BATCH) == 0 && > > AFAICS, zone_page_state will correct negative values to zero only for > CONFIG_SMP. Won't this check be broken on !CONFIG_SMP? > On !CONFIG_SMP how can there be per-cpu accounting drift that would make that counter negative? -- Mel Gorman SUSE Labs -- 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