From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH 07/12] migration: hold the lock only if it is really needed Date: Tue, 3 Jul 2018 14:27:01 +0800 Message-ID: <4e365b59-9859-c5b6-5d45-7940507eb7a9@gmail.com> References: <20180604095520.8563-1-xiaoguangrong@tencent.com> <20180604095520.8563-8-xiaoguangrong@tencent.com> <20180619073650.GB14814@xz-mi> <5745f752-50b5-0645-21a7-3336ea0dd5c2@gmail.com> <20180629112224.GG2568@work-vm> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, mst@redhat.com, mtosatti@redhat.com, Xiao Guangrong , qemu-devel@nongnu.org, Peter Xu , wei.w.wang@intel.com, jiang.biao2@zte.com.cn, pbonzini@redhat.com To: "Dr. David Alan Gilbert" Return-path: In-Reply-To: <20180629112224.GG2568@work-vm> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On 06/29/2018 07:22 PM, Dr. David Alan Gilbert wrote: > * Xiao Guangrong (guangrong.xiao@gmail.com) wrote: >> >> >> On 06/19/2018 03:36 PM, Peter Xu wrote: >>> On Mon, Jun 04, 2018 at 05:55:15PM +0800, guangrong.xiao@gmail.com wrote: >>>> From: Xiao Guangrong >>>> >>>> Try to hold src_page_req_mutex only if the queue is not >>>> empty >>> >>> Pure question: how much this patch would help? Basically if you are >>> running compression tests then I think it means you are with precopy >>> (since postcopy cannot work with compression yet), then here the lock >>> has no contention at all. >> >> Yes, you are right, however we can observe it is in the top functions >> (after revert this patch): > > Can you show the matching trace with the patch in? Sure, there is: + 8.38% kqemu [kernel.kallsyms] [k] copy_user_enhanced_fast_string + 8.03% kqemu qemu-system-x86_64 [.] ram_bytes_total + 6.62% kqemu qemu-system-x86_64 [.] qemu_event_set + 6.02% kqemu qemu-system-x86_64 [.] qemu_put_qemu_file + 5.81% kqemu qemu-system-x86_64 [.] __ring_put + 5.04% kqemu qemu-system-x86_64 [.] compress_thread_data_done + 4.48% kqemu qemu-system-x86_64 [.] ring_is_full + 4.44% kqemu qemu-system-x86_64 [.] ring_mp_get + 3.39% kqemu qemu-system-x86_64 [.] __ring_is_full + 2.61% kqemu qemu-system-x86_64 [.] add_to_iovec + 2.48% kqemu qemu-system-x86_64 [.] threads_submit_request_prepare + 2.08% kqemu libc-2.12.so [.] memcpy + 2.07% kqemu qemu-system-x86_64 [.] ring_len + 1.91% kqemu [kernel.kallsyms] [k] __lock_acquire + 1.60% kqemu qemu-system-x86_64 [.] buffer_zero_sse2 + 1.16% kqemu qemu-system-x86_64 [.] ram_find_and_save_block + 1.14% kqemu qemu-system-x86_64 [.] ram_save_target_page + 1.12% kqemu qemu-system-x86_64 [.] compress_page_with_multi_thread + 1.09% kqemu qemu-system-x86_64 [.] ram_save_host_page + 1.07% kqemu qemu-system-x86_64 [.] test_and_clear_bit + 1.07% kqemu qemu-system-x86_64 [.] qemu_put_buffer + 1.03% kqemu qemu-system-x86_64 [.] qemu_put_byte + 0.80% kqemu qemu-system-x86_64 [.] threads_submit_request_commit + 0.74% kqemu qemu-system-x86_64 [.] migration_bitmap_clear_dirty + 0.70% kqemu qemu-system-x86_64 [.] control_save_page + 0.69% kqemu qemu-system-x86_64 [.] test_bit + 0.69% kqemu qemu-system-x86_64 [.] ram_save_iterate + 0.63% kqemu qemu-system-x86_64 [.] migration_bitmap_find_dirty + 0.63% kqemu qemu-system-x86_64 [.] ram_control_save_page + 0.62% kqemu qemu-system-x86_64 [.] rcu_read_lock + 0.56% kqemu qemu-system-x86_64 [.] qemu_file_get_error + 0.55% kqemu [kernel.kallsyms] [k] lock_acquire + 0.55% kqemu qemu-system-x86_64 [.] find_dirty_block + 0.54% kqemu qemu-system-x86_64 [.] ring_index + 0.53% kqemu qemu-system-x86_64 [.] ring_put + 0.51% kqemu qemu-system-x86_64 [.] unqueue_page + 0.50% kqemu qemu-system-x86_64 [.] migrate_use_compression + 0.48% kqemu qemu-system-x86_64 [.] get_queued_page + 0.46% kqemu qemu-system-x86_64 [.] ring_get + 0.46% kqemu [i40e] [k] i40e_clean_tx_irq + 0.45% kqemu [kernel.kallsyms] [k] lock_release + 0.44% kqemu [kernel.kallsyms] [k] native_sched_clock + 0.38% kqemu qemu-system-x86_64 [.] migrate_get_current + 0.38% kqemu [kernel.kallsyms] [k] find_held_lock + 0.34% kqemu [kernel.kallsyms] [k] __lock_release + 0.34% kqemu qemu-system-x86_64 [.] qemu_ram_pagesize + 0.29% kqemu [kernel.kallsyms] [k] lock_is_held_type + 0.27% kqemu [kernel.kallsyms] [k] update_load_avg + 0.27% kqemu qemu-system-x86_64 [.] save_page_use_compression + 0.24% kqemu qemu-system-x86_64 [.] qemu_file_rate_limit + 0.23% kqemu [kernel.kallsyms] [k] tcp_sendmsg + 0.23% kqemu [kernel.kallsyms] [k] match_held_lock + 0.22% kqemu [kernel.kallsyms] [k] do_raw_spin_trylock + 0.22% kqemu [kernel.kallsyms] [k] cyc2ns_read_begin