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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id b74sm327032qkc.17.2020.05.26.11.15.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2020 11:15:02 -0700 (PDT) Date: Tue, 26 May 2020 14:14:59 -0400 From: Qian Cai To: Feng Tang Cc: Andrew Morton , Michal Hocko , Johannes Weiner , Stephen Rothwell , Matthew Wilcox , Mel Gorman , Kees Cook , Luis Chamberlain , Iurii Zaikin , andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] make vm_committed_as_batch aware of vm overcommit policy Message-ID: <20200526181459.GD991@lca.pw> References: <1588922717-63697-1-git-send-email-feng.tang@intel.com> <20200521212726.GC6367@ovpn-112-192.phx2.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200521212726.GC6367@ovpn-112-192.phx2.redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2020 at 05:27:26PM -0400, Qian Cai wrote: > On Fri, May 08, 2020 at 03:25:14PM +0800, Feng Tang wrote: > > When checking a performance change for will-it-scale scalability > > mmap test [1], we found very high lock contention for spinlock of > > percpu counter 'vm_committed_as': > > > > 94.14% 0.35% [kernel.kallsyms] [k] _raw_spin_lock_irqsave > > 48.21% _raw_spin_lock_irqsave;percpu_counter_add_batch;__vm_enough_memory;mmap_region;do_mmap; > > 45.91% _raw_spin_lock_irqsave;percpu_counter_add_batch;__do_munmap; > > > > Actually this heavy lock contention is not always necessary. The > > 'vm_committed_as' needs to be very precise when the strict > > OVERCOMMIT_NEVER policy is set, which requires a rather small batch > > number for the percpu counter. > > > > So lift the batch number to 16X for OVERCOMMIT_ALWAYS and > > OVERCOMMIT_GUESS policies, and add a sysctl handler to adjust it > > when the policy is reconfigured. > > > > Benchmark with the same testcase in [1] shows 53% improvement on a > > 8C/16T desktop, and 2097%(20X) on a 4S/72C/144T server. And no change > > for some platforms, due to the test mmap size of the case is bigger > > than the batch number computed, though the patch will help mmap/munmap > > generally. > > > > [1] https://lkml.org/lkml/2020/3/5/57 > > > > There are some style complain from checkpatch for patch 3, as it > > follows the similar format of sibling functions > > > > patch1: a cleanup for /proc/meminfo > > patch2: a preparation patch which also improve the accuracy of > > vm_memory_committed > > patch3: the main change > > > > Please help to review, thanks! > > Reverted this series fixed a warning under memory pressue. Andrew, Stephen, can you drop this series? > > [ 3319.257898] LTP: starting oom01 > [ 3319.284417] ------------[ cut here ]------------ > [ 3319.284439] memory commitment underflow > [ 3319.284456] WARNING: CPU: 13 PID: 130949 at mm/util.c:835 __vm_enough_memory+0x1dc/0x1f0 > [ 3319.284485] Modules linked in: brd ext4 crc16 mbcache jbd2 loop kvm_hv kvm ip_tables x_tables xfs sd_mod ahci libahci bnx2x libata mdio tg3 libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod > [ 3319.284538] CPU: 13 PID: 130949 Comm: oom01 Not tainted 5.7.0-rc6-next-20200521+ #115 > [ 3319.284551] NIP: c00000000043027c LR: c000000000430278 CTR: c0000000007bd120 > [ 3319.284572] REGS: c00000064a42f710 TRAP: 0700 Not tainted (5.7.0-rc6-next-20200521+) > [ 3319.284602] MSR: 900000000282b033 CR: 28222422 XER: 20040000 > [ 3319.284638] CFAR: c000000000119098 IRQMASK: 0 > GPR00: c000000000430278 c00000064a42f9a0 c000000001765500 000000000000001b > GPR04: c00000000179c3b0 000000000000000b 0000000066726564 c00000000429ac28 > GPR08: 0000000000000001 0000000000000000 0000000000000000 c000001301facc80 > GPR12: 0000000000002000 c000001fffff3d80 0000000000000000 0000000000000000 > GPR16: 0000000000000000 0000000000000000 c0000014f358dd60 fffffffffff7dfff > GPR20: c0000003725a9128 c0000003725a3928 c000000b0a0c0670 c000000b0a0c0678 > GPR24: c000000b0a0c0660 c00000064a42fa58 c000000b0a0c0650 c0000003725a9080 > GPR28: 0000000000000001 0000000000000000 c000000001620178 0000000000000001 > [ 3319.284825] NIP [c00000000043027c] __vm_enough_memory+0x1dc/0x1f0 > [ 3319.284853] LR [c000000000430278] __vm_enough_memory+0x1d8/0x1f0 > [ 3319.284872] Call Trace: > [ 3319.284889] [c00000064a42f9a0] [c000000000430278] __vm_enough_memory+0x1d8/0x1f0 (unreliable) > [ 3319.284930] [c00000064a42fa30] [c000000000114258] dup_mm+0x2a8/0x700 > [ 3319.284960] [c00000064a42fae0] [c000000000115c7c] copy_process+0xeac/0x1a00 > [ 3319.284981] [c00000064a42fbf0] [c000000000116b3c] _do_fork+0xac/0xce0 > [ 3319.285002] [c00000064a42fd00] [c000000000117928] __do_sys_clone+0x98/0xe0 > [ 3319.285032] [c00000064a42fdc0] [c000000000039e78] system_call_exception+0x108/0x1d0 > [ 3319.285064] [c00000064a42fe20] [c00000000000c9f0] system_call_common+0xf0/0x278 > [ 3319.285093] Instruction dump: > [ 3319.285109] 60000000 73a90001 4182000c e8be0002 4bfffeb8 3c62ff51 39200001 3d42fff9 > [ 3319.285142] 38636690 992a6ad6 4bce8dbd 60000000 <0fe00000> e8be0002 4bfffe90 60000000 > [ 3319.285166] irq event stamp: 0 > [ 3319.285183] hardirqs last enabled at (0): [<0000000000000000>] 0x0 > [ 3319.285195] hardirqs last disabled at (0): [] copy_process+0x6f8/0x1a00 > [ 3319.285216] softirqs last enabled at (0): [] copy_process+0x6f8/0x1a00 > [ 3319.285238] softirqs last disabled at (0): [<0000000000000000>] 0x0 > [ 3319.285267] ---[ end trace 115e3f7fbb0653c2 ]--- > > > > > - Feng > > > > ---------------------------------------------------------------- > > Changelog: > > v2: > > * add the sysctl handler to cover runtime overcommit policy > > change, as suggested by Andres Morton > > * address the accuracy concern of vm_memory_committed() > > from Andi Kleen > > > > Feng Tang (3): > > proc/meminfo: avoid open coded reading of vm_committed_as > > mm/util.c: make vm_memory_committed() more accurate > > mm: adjust vm_committed_as_batch according to vm overcommit policy > > > > fs/proc/meminfo.c | 2 +- > > include/linux/mm.h | 2 ++ > > include/linux/mman.h | 4 ++++ > > kernel/sysctl.c | 2 +- > > mm/mm_init.c | 19 +++++++++++++++---- > > mm/util.c | 15 ++++++++++++++- > > 6 files changed, 37 insertions(+), 7 deletions(-) > > > > -- > > 2.7.4 > > > >