From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Kenneth W" Subject: RE: slow hugetlb from 2.6.15 Date: Tue, 27 Jun 2006 12:23:10 -0700 Message-ID: <000001c69a1f$2171af00$e234030a@amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit In-Reply-To: <1151434062.8918.7.camel@dyn9047017100.beaverton.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: 'Badari Pulavarty' , stanojr@blackhole.websupport.sk Cc: linux-mm List-ID: Badari Pulavarty wrote on Tuesday, June 27, 2006 11:48 AM > On Tue, 2006-06-27 at 20:23 +0200, stanojr@blackhole.websupport.sk wrote: > > hello > > > > look at this benchmark http://www-unix.mcs.anl.gov/~kazutomo/hugepage/note.html > > i try benchmark it on latest 2.6.17.1 (x86 and x86_64) and it slow like 2.6.16 > > on that web (in comparing to standard 4kb page) > > its feature or bug ? > > Most likely, its due to new feature - demand paging for large pages :) > Doing mlock() on mmaped area help ? The original code measures not only the access time, but also page fault path, that explains the huge difference with hugetlb between 2.6.12 and 2.6.16. The former kernel prefaults, thus fault time is all done at mmap call and is not counted at all in the timing measurement, while the latter measurement includes faulting of hugetlb page. Though it is a mystery to see that faulting on hugetlb page is significantly longer than faulting a normal page. Yes, mlock() would take the variation out of the equation (if such call is made outside the measurement). - Ken -- 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