Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755157AbbKDHrJ (ORCPT ); Wed, 4 Nov 2015 02:47:09 -0500 Received: from mga09.intel.com ([134.134.136.24]:44205 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754494AbbKDHrH (ORCPT ); Wed, 4 Nov 2015 02:47:07 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,241,1444719600"; d="scan'208";a="842203825" From: "Huang\, Ying" To: Hugh Dickins Cc: Andrew Morton , Josef Bacik , Yu Zhao , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] tmpfs: avoid a little creat and stat slowdown References: Date: Wed, 04 Nov 2015 15:47:03 +0800 In-Reply-To: (Hugh Dickins's message of "Thu, 29 Oct 2015 12:13:35 -0700 (PDT)") Message-ID: <87bnbagqa0.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6400 Lines: 94 Hugh Dickins writes: > LKP reports that v4.2 commit afa2db2fb6f1 ("tmpfs: truncate prealloc > blocks past i_size") causes a 14.5% slowdown in the AIM9 creat-clo > benchmark. > > creat-clo does just what you'd expect from the name, and creat's O_TRUNC > on 0-length file does indeed get into more overhead now shmem_setattr() > tests "0 <= 0" instead of "0 < 0". > > I'm not sure how much we care, but I think it would not be too VW-like > to add in a check for whether any pages (or swap) are allocated: if none > are allocated, there's none to remove from the radix_tree. At first I > thought that check would be good enough for the unmaps too, but no: we > should not skip the unlikely case of unmapping pages beyond the new EOF, > which were COWed from holes which have now been reclaimed, leaving none. > > This gives me an 8.5% speedup: on Haswell instead of LKP's Westmere, > and running a debug config before and after: I hope those account for > the lesser speedup. > > And probably someone has a benchmark where a thousand threads keep on > stat'ing the same file repeatedly: forestall that report by adjusting > v4.3 commit 44a30220bc0a ("shmem: recalculate file inode when fstat") > not to take the spinlock in shmem_getattr() when there's no work to do. > > Reported-by: Ying Huang > Signed-off-by: Hugh Dickins Hi, Hugh, Thanks a lot for your support! The test on LKP shows that this patch restores a big part of the regression! In following list, c435a390574d012f8d30074135d8fcc6f480b484: is parent commit afa2db2fb6f15f860069de94a1257db57589fe95: is the first bad commit has performance regression. 43819159da2b77fedcf7562134d6003dccd6a068: is the fixing patch ========================================================================================= compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime: gcc-4.9/performance/x86_64-rhel/debian-x86_64-2015-02-07.cgz/lkp-wsx02/creat-clo/aim9/300s commit: c435a390574d012f8d30074135d8fcc6f480b484 afa2db2fb6f15f860069de94a1257db57589fe95 43819159da2b77fedcf7562134d6003dccd6a068 c435a390574d012f afa2db2fb6f15f860069de94a1 43819159da2b77fedcf7562134 ---------------- -------------------------- -------------------------- %stddev %change %stddev %change %stddev \ | \ | \ 563556 ± 1% -12.5% 493033 ± 5% -5.6% 531968 ± 1% aim9.creat-clo.ops_per_sec 11836 ± 7% +11.4% 13184 ± 7% +15.0% 13608 ± 5% numa-meminfo.node1.SReclaimable 10121526 ± 3% -12.1% 8897097 ± 5% -4.1% 9707953 ± 4% proc-vmstat.pgalloc_normal 9.34 ± 4% -11.4% 8.28 ± 3% -4.8% 8.88 ± 2% time.user_time 3480 ± 3% -2.5% 3395 ± 1% -28.5% 2488 ± 3% vmstat.system.cs 203275 ± 17% -6.8% 189453 ± 5% -34.4% 133352 ± 11% cpuidle.C1-NHM.usage 8081280 ±129% -93.3% 538377 ± 97% +31.5% 10625496 ±106% cpuidle.C1E-NHM.time 3144 ± 58% +619.0% 22606 ± 56% +903.9% 31563 ± 0% numa-vmstat.node0.numa_other 2958 ± 7% +11.4% 3295 ± 7% +15.0% 3401 ± 5% numa-vmstat.node1.nr_slab_reclaimable 45074 ± 5% -43.4% 25494 ± 57% -68.7% 14105 ± 2% numa-vmstat.node2.numa_other 56140 ± 0% +0.0% 56158 ± 0% -94.4% 3120 ± 0% slabinfo.Acpi-ParseExt.active_objs 1002 ± 0% +0.0% 1002 ± 0% -92.0% 80.00 ± 0% slabinfo.Acpi-ParseExt.active_slabs 56140 ± 0% +0.0% 56158 ± 0% -94.4% 3120 ± 0% slabinfo.Acpi-ParseExt.num_objs 1002 ± 0% +0.0% 1002 ± 0% -92.0% 80.00 ± 0% slabinfo.Acpi-ParseExt.num_slabs 1079 ± 5% -10.8% 962.00 ± 10% -100.0% 0.00 ± -1% slabinfo.blkdev_ioc.active_objs 1079 ± 5% -10.8% 962.00 ± 10% -100.0% 0.00 ± -1% slabinfo.blkdev_ioc.num_objs 110.67 ± 39% +74.4% 193.00 ± 46% +317.5% 462.00 ± 8% slabinfo.blkdev_queue.active_objs 189.33 ± 23% +43.7% 272.00 ± 33% +151.4% 476.00 ± 10% slabinfo.blkdev_queue.num_objs 1129 ± 10% -1.9% 1107 ± 7% +20.8% 1364 ± 6% slabinfo.blkdev_requests.active_objs 1129 ± 10% -1.9% 1107 ± 7% +20.8% 1364 ± 6% slabinfo.blkdev_requests.num_objs 1058 ± 3% -10.3% 949.00 ± 9% -100.0% 0.00 ± -1% slabinfo.file_lock_ctx.active_objs 1058 ± 3% -10.3% 949.00 ± 9% -100.0% 0.00 ± -1% slabinfo.file_lock_ctx.num_objs 4060 ± 1% -2.1% 3973 ± 1% -10.5% 3632 ± 1% slabinfo.files_cache.active_objs 4060 ± 1% -2.1% 3973 ± 1% -10.5% 3632 ± 1% slabinfo.files_cache.num_objs 10001 ± 0% -0.3% 9973 ± 0% -61.1% 3888 ± 0% slabinfo.ftrace_event_field.active_objs 10001 ± 0% -0.3% 9973 ± 0% -61.1% 3888 ± 0% slabinfo.ftrace_event_field.num_objs 1832 ± 0% +0.4% 1840 ± 0% -100.0% 0.00 ± -1% slabinfo.ftrace_event_file.active_objs 1832 ± 0% +0.4% 1840 ± 0% -100.0% 0.00 ± -1% slabinfo.ftrace_event_file.num_objs 1491 ± 5% -2.3% 1456 ± 6% +12.0% 1669 ± 4% slabinfo.mnt_cache.active_objs 1491 ± 5% -2.3% 1456 ± 6% +12.0% 1669 ± 4% slabinfo.mnt_cache.num_objs 126.33 ± 19% +10.2% 139.17 ± 9% -100.0% 0.00 ± -1% slabinfo.nfs_commit_data.active_objs 126.33 ± 19% +10.2% 139.17 ± 9% -100.0% 0.00 ± -1% slabinfo.nfs_commit_data.num_objs 97.17 ± 20% -9.1% 88.33 ± 28% -100.0% 0.00 ± -1% slabinfo.user_namespace.active_objs 97.17 ± 20% -9.1% 88.33 ± 28% -100.0% 0.00 ± -1% slabinfo.user_namespace.num_objs Best Regards, Huang, Ying -- 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/