linux-kernel - Re: rq lock contention due to commit af7f588d8f73

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Date:   Tue, 28 Mar 2023 08:39:41 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Aaron Lu <aaron.lu@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: rq lock contention due to commit af7f588d8f73

On 2023-03-28 02:58, Aaron Lu wrote:
> On Mon, Mar 27, 2023 at 03:57:43PM -0400, Mathieu Desnoyers wrote:
>   
>> I've just resuscitated my per-runqueue concurrency ID cache patch from an older
>> patchset, and posted it as RFC. So far it passed one round of rseq selftests. Can
>> you test it in your environment to see if I'm on the right track ?
>>
>> https://lore.kernel.org/lkml/20230327195318.137094-1-mathieu.desnoyers@efficios.com/
> 
> There are improvements with this patch.
> 
> When running the client side sysbench with nr_thread=56, the lock contention
> is gone%; with nr_thread=224(=nr_cpu of this machine), the lock contention
> dropped from 75% to 27%.

This is a good start!

Can you compare this with Peter's approach to modify init/Kconfig, make 
SCHED_MM_CID a bool, and set it =n in the kernel config ?

I just want to see what baseline we should compare against.

Another test we would want to try here: there is an arbitrary choice for 
the runqueue cache array size in my own patch:

kernel/sched/sched.h:
# define RQ_CID_CACHE_SIZE    8

Can you try changing this value for 16 or 32 instead and see if it helps?

Thanks,

Mathieu

> 
> v6.3.0-rc4:
> 
>      75.21%    75.20%  [kernel.vmlinux]          [k] native_queued_spin_lock_slowpath
> 37.30% native_queued_spin_lock_slowpath;_raw_spin_lock;__schedule;schedule;schedule_hrtimeout_range_clock;schedule_hrtimeout_range;do_sys_poll;__x64_sys_poll;do_syscall_64;entry_SYSCALL_64_after_hwframe;__poll;0x7f943d6fcff8;PQgetResult;0x7f943d6f9a2b;0x55c7f9bde88b
> 26.01% native_queued_spin_lock_slowpath;_raw_spin_lock;__schedule;schedule_idle;do_idle;cpu_startup_entry;start_secondary;secondary_startup_64_no_verify
> 11.36% native_queued_spin_lock_slowpath;_raw_spin_lock;__schedule;schedule;schedule_hrtimeout_range_clock;schedule_hrtimeout_range;do_epoll_wait;__x64_sys_epoll_wait;do_syscall_64;entry_SYSCALL_64_after_hwframe;epoll_wait;secure_read;0x55c4d1363867;pq_getbyte;PostgresMain;0x55c4d140c828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 
> v6.3.0-rc4+the_above_patch:
> 
>      27.86%    27.85%  [kernel.vmlinux]            [k] native_queued_spin_lock_slowpath
> 7.31% native_queued_spin_lock_slowpath;_raw_spin_lock;try_to_wake_up;default_wake_function;pollwake;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send;0x5637a602e4cd;0x5637a602e98d;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 4.62% native_queued_spin_lock_slowpath;_raw_spin_lock;__schedule;schedule_idle;do_idle;cpu_startup_entry;start_secondary;secondary_startup_64_no_verify
> 4.20% native_queued_spin_lock_slowpath;_raw_spin_lock;__schedule;schedule;schedule_hrtimeout_range_clock;schedule_hrtimeout_range;do_epoll_wait;__x64_sys_epoll_wait;do_syscall_64;entry_SYSCALL_64;epoll_wait;secure_read;0x5637a602e867;pq_getbyte;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 1.66% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;_raw_spin_rq_lock_irqsave;try_to_wake_up;default_wake_function;ep_autoremove_wake_function;__wake_up_common;__wake_up_common_lock;__wake_up;ep_poll_callback;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send
> 1.65% native_queued_spin_lock_slowpath;_raw_spin_lock;try_to_wake_up;default_wake_function;pollwake;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_data_queue;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send;0x5637a602e4cd;0x5637a602e69e;0x5637a602e7ae;0x5637a5e5f62e;standard_ExecutorRun;0x5637a615abeb;PortalRun;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 1.63% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;__schedule;schedule;schedule_hrtimeout_range_clock;schedule_hrtimeout_range;do_epoll_wait;__x64_sys_epoll_wait;do_syscall_64;entry_SYSCALL_64;epoll_wait;secure_read;0x5637a602e867;pq_getbyte;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 1.40% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;try_to_wake_up;default_wake_function;pollwake;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send;0x5637a602e4cd;0x5637a602e98d;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 1.20% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;_raw_spin_rq_lock_irqsave;try_to_wake_up;default_wake_function;pollwake;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send;0x5637a602e4cd;0x5637a602e98d;PostgresMain;0x5637a60d7828;PostmasterMain;main;__libc_start_main;0x5541d68949564100
> 0.83% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;__task_rq_lock;try_to_wake_up;default_wake_function;ep_autoremove_wake_function;__wake_up_common;__wake_up_common_lock;__wake_up;ep_poll_callback;__wake_up_common;__wake_up_common_lock;__wake_up_sync_key;sock_def_readable;tcp_data_ready;tcp_rcv_established;tcp_v4_do_rcv;tcp_v4_rcv;ip_protocol_deliver_rcu;ip_local_deliver_finish;ip_local_deliver;ip_rcv;__netif_receive_skb_one_core;__netif_receive_skb;process_backlog;__napi_poll;net_rx_action;__do_softirq;do_softirq.part.0;__local_bh_enable_ip;ip_finish_output2;__ip_finish_output;ip_finish_output;ip_output;ip_local_out;__ip_queue_xmit;ip_queue_xmit;__tcp_transmit_skb;tcp_write_xmit;__tcp_push_pending_frames;tcp_push;tcp_sendmsg_locked;tcp_sendmsg;inet_sendmsg;sock_sendmsg;__sys_sendto;__x64_sys_sendto;do_syscall_64;entry_SYSCALL_64;__libc_send
> 0.65% native_queued_spin_lock_slowpath;_raw_spin_lock;raw_spin_rq_lock_nested;__schedule;schedule_idle;do_idle;cpu_startup_entry;start_secondary;secondary_startup_64_no_verify

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com