Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760121AbZDHBRo (ORCPT ); Tue, 7 Apr 2009 21:17:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756382AbZDHBRd (ORCPT ); Tue, 7 Apr 2009 21:17:33 -0400 Received: from smtp-out.google.com ([216.239.33.17]:27899 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755864AbZDHBRc (ORCPT ); Tue, 7 Apr 2009 21:17:32 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=uZ8pb7nCvzcgSTXn2/2vOF+72aCeURLU6dWc0IXo070kZQ0DfnJEAKZ6QKy+PQVfD amMmZFsHvX5ra+B7as5Gg== MIME-Version: 1.0 In-Reply-To: <20090407232700.GB5607@localhost> References: <20090407071729.233579162@intel.com> <20090407072133.053995305@intel.com> <604427e00904071303g1d092eabp59fca0713ddacf82@mail.gmail.com> <20090407232700.GB5607@localhost> Date: Tue, 7 Apr 2009 18:17:26 -0700 Message-ID: <604427e00904071817n767122byb439043e8a228011@mail.gmail.com> Subject: Re: [PATCH 03/14] mm: remove FAULT_FLAG_RETRY dead code From: Ying Han To: Wu Fengguang Cc: Andrew Morton , LKML , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5334 Lines: 146 On Tue, Apr 7, 2009 at 4:27 PM, Wu Fengguang wrote: > On Wed, Apr 08, 2009 at 04:03:36AM +0800, Ying Han wrote: >> On Tue, Apr 7, 2009 at 12:17 AM, Wu Fengguang wrote: >> > Cc: Ying Han >> > Signed-off-by: Wu Fengguang >> > --- >> > mm/memory.c | 4 +--- >> > 1 file changed, 1 insertion(+), 3 deletions(-) >> > >> > --- mm.orig/mm/memory.c >> > +++ mm/mm/memory.c >> > @@ -2766,10 +2766,8 @@ static int do_linear_fault(struct mm_str >> > { >> > pgoff_t pgoff = (((address & PAGE_MASK) >> > - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; >> > - int write = write_access & ~FAULT_FLAG_RETRY; >> > - unsigned int flags = (write ? FAULT_FLAG_WRITE : 0); >> > + unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0); >> > >> > - flags |= (write_access & FAULT_FLAG_RETRY); >> > pte_unmap(page_table); >> > return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); >> > } >> So, we got rid of FAULT_FLAG_RETRY flag? > > Seems yes for the current mm tree, see the following two commits. > > I did this patch on seeing 761fe7bc8193b7. But a closer look > indicates that the following two patches disable the filemap > VM_FAULT_RETRY part totally... > > Anyway, if these two patches are to be reverted somehow(I guess yes), > this patch shall be _ignored_. > > btw, do you have any test case and performance numbers for > FAULT_FLAG_RETRY? And possible overheads for (the worst case) > sparse random mmap reads on a sparse file? I cannot find any > in your changelogs.. here is the benchmark i posted on [V1] but somehow missed in [V2] describtion Benchmarks: case 1. one application has a high count of threads each faulting in different pages of a hugefile. Benchmark indicate that this double data structure walking in case of major fault results in << 1% performance hit. case 2. add another thread in the above application which in a tight loop of mmap()/munmap(). Here we measure loop count in the new thread while other threads doing the same amount of work as case one. we got << 3% performance hit on the Complete Time(benchmark value for case one) and 10% performance improvement on the mmap()/munmap() counter. This patch helps a lot in cases we have writer which is waitting behind all readers, so it could execute much faster. --Ying > > Thanks, > Fengguang > > > commit 761fe7bc8193b7858b7dc7eb4a026dc66e49fe1f > Author: Andrew Morton > Date: Mon Feb 9 21:08:50 2009 +0100 > > A shot in the dark :( > > Cc: Mike Waychison > Cc: Ying Han > Signed-off-by: Andrew Morton > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index bac7d7a..1c6736d 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -1139,8 +1139,6 @@ good_area: > return; > } > > - write |= retry_flag; > - > /* > * If for any reason at all we couldn't handle the fault, > * make sure we exit gracefully rather than endlessly redo > > > commit f01ca7a68c37680a4eee22a8722a713c5102b3bb > Author: Andrew Morton > Date: Mon Feb 9 21:08:50 2009 +0100 > > Untangle the `write' boolean from the FAULT_FLAG_foo non-boolean field. > > Cc: "H. Peter Anvin" > Cc: Benjamin Herrenschmidt > Cc: David Rientjes > Cc: Hugh Dickins > Cc: Ingo Molnar > Cc: Lee Schermerhorn > Cc: Mike Waychison > Cc: Nick Piggin > Cc: Peter Zijlstra > Cc: Rohit Seth > Cc: Trk Edwin > Cc: Valdis.Kletnieks@vt.edu > Cc: Ying Han > Signed-off-by: Andrew Morton > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index b2cc88f..bac7d7a 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -978,7 +978,7 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code) > struct mm_struct *mm; > int write; > int fault; > - unsigned int retry_flag = FAULT_FLAG_RETRY; > + int retry_flag = 1; > > tsk = current; > mm = tsk->mm; > @@ -1140,6 +1140,7 @@ good_area: > } > > write |= retry_flag; > + > /* > * If for any reason at all we couldn't handle the fault, > * make sure we exit gracefully rather than endlessly redo > @@ -1159,8 +1160,8 @@ good_area: > * be removed or changed after the retry. > */ > if (fault & VM_FAULT_RETRY) { > - if (write & FAULT_FLAG_RETRY) { > - retry_flag &= ~FAULT_FLAG_RETRY; > + if (retry_flag) { > + retry_flag = 0; > goto retry; > } > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/