From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id DAE096B0169 for ; Sat, 13 Aug 2011 19:56:18 -0400 (EDT) Date: Sun, 14 Aug 2011 01:56:11 +0200 From: Andrea Arcangeli Subject: Re: [RFC PATCH 0/3] page count lock for simpler put_page Message-ID: <20110813235611.GA16581@redhat.com> References: <1312492042-13184-1-git-send-email-walken@google.com> <20110807142532.GC1823@barrios-desktop> <20110812153616.GH7959@redhat.com> <20110812160813.GF2395@linux.vnet.ibm.com> <20110812164325.GK7959@redhat.com> <20110812172758.GL2395@linux.vnet.ibm.com> <20110813015741.GZ2395@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110813015741.GZ2395@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Paul E. McKenney" Cc: Michel Lespinasse , Minchan Kim , Hugh Dickins , linux-mm@kvack.org, Andrew Morton , Rik van Riel , Mel Gorman , Johannes Weiner , KOSAKI Motohiro , Shaohua Li On Fri, Aug 12, 2011 at 06:57:41PM -0700, Paul E. McKenney wrote: > But if we are getting much below 100 milliseconds, we need to rethink > this. The delay may be low in some corner case but this still benefits by running it only once. You can mmap() bzero, mremap(+4096) (if mremap moves the pages to a not aligned 2m address, it forces a split_huge_page, an hardware issue) and all pages will be splitted in potentially less than 100msec if they're only a few. At least we'll be running synchronize_rcu only once instead of for every hugepage, as long as it runs only once I guess we're ok. Normally it shouldn't happen so fast. My current /proc/vmstat says there are 271 splits for 97251 THP allocated and they're not so likely to have happened within 100msec. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org