From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 651AD5F0001 for ; Thu, 9 Apr 2009 03:37:22 -0400 (EDT) Date: Thu, 9 Apr 2009 15:36:20 +0800 From: Wu Fengguang Subject: Re: [PATCH][0/2]page_fault retry with NOPAGE_RETRY Message-ID: <20090409073620.GA31527@localhost> References: <604427e00904081302p7aad170bu5ff0702415455f7@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <604427e00904081302p7aad170bu5ff0702415455f7@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Ying Han Cc: "linux-mm@kvack.org" , linux-kernel , akpm , "torvalds@linux-foundation.org" , Ingo Molnar , Mike Waychison , Rohit Seth , Hugh Dickins , Peter Zijlstra , "H. Peter Anvin" , =?utf-8?B?VMO2csO2aw==?= Edwin , Lee Schermerhorn , Nick Piggin List-ID: Hi Ying, //Nitpicks on the changlog.. On Thu, Apr 09, 2009 at 04:02:23AM +0800, Ying Han wrote: > changelog[v3]: > - applied fixes and cleanups from Wu Fengguang. > filemap VM_FAULT_RETRY fixes > [PATCH 01/14] mm: fix find_lock_page_retry() return value parsing > [PATCH 02/14] mm: fix major/minor fault accounting on retried fault > [PATCH 04/14] mm: reduce duplicate page fault code > [PATCH 05/14] readahead: account mmap_miss for VM_FAULT_RETRY > > - split the patch into two parts. first part includes FAULT_FLAG_RETRY > support with no current user change. second part includes individual > per-architecture cleanups that enable FAULT_FLAG_RETRY. > currently there are mainly two users for handle_mm_fault, we enable > FAULT_FLAG_RETRY for actual fault handler and leave get_user_pages > unchanged. The below benchmarks can also go into changelog of patch 01. Besides, there you should also explain the problem and approach, the _benefited_ workloads and how/how much they will benefit, the _hurt_ workloads and how they are impacted and the bound of overheads. > Benchmarks: > posted on [V1]: > 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. > > some new test results from Wufengguang: > Just tested the sparse-random-read-on-sparse-file case, and found the > performance impact to be 0.4% (8.706s vs 8.744s). Kind of acceptable. the 0.4% here should be the worst case overheads. > without FAULT_FLAG_RETRY: > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.28s user > 5.39s system 99% cpu 8.692 total > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.17s user > 5.54s system 99% cpu 8.742 total > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.18s user > 5.48s system 99% cpu 8.684 total ugly line wraps > FAULT_FLAG_RETRY: > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.18s user > 5.63s system 99% cpu 8.825 total > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.22s user > 5.47s system 99% cpu 8.718 total > iotrace.rb --load stride-100 --mplay /mnt/btrfs-ram/sparse 3.13s user > 5.55s system 99% cpu 8.690 total ditto Thanks, Fengguang > In the above faked workload, the mmap read page offsets are loaded from > stride-100 and performed on /mnt/btrfs-ram/sparse, which are created by: > > seq 0 100 1000000 > stride-100 > dd if=/dev/zero of=/mnt/btrfs-ram/sparse bs=1M count=1 seek=1024000 > > Signed-off-by: Ying Han > Mike Waychison > > arch/x86/mm/fault.c | 20 ++++++++++++++ > include/linux/fs.h | 2 +- > include/linux/mm.h | 2 + > mm/filemap.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++-- > mm/memory.c | 33 +++++++++++++++++------ > 5 files changed, 116 insertions(+), 13 deletions(-) -- 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