From: Mike Galbraith <efault@gmx.de>
To: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Suresh Siddha <suresh.b.siddha@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue()
Date: Wed, 03 Oct 2012 15:30:01 +0200 [thread overview]
Message-ID: <1349271001.4465.66.camel@marge.simpson.net> (raw)
In-Reply-To: <1349251997.4465.42.camel@marge.simpson.net>
On Wed, 2012-10-03 at 10:13 +0200, Mike Galbraith wrote:
> Watching all cores instead.
>
> switch rate ~890KHz switch rate ~570KHz
> NO_TTWU_QUEUE nohz=off TTWU_QUEUE nohz=off
> 5.38% [kernel] [k] __schedule 4.81% [kernel] [k] _raw_spin_lock_irqsave
> 4.29% [kernel] [k] _raw_spin_lock_irqsave 3.36% [kernel] [k] __skb_recv_datagram
> 2.88% [kernel] [k] resched_task 2.71% [kernel] [k] copy_user_generic_string
> 2.60% [kernel] [k] copy_user_generic_string 2.67% [kernel] [k] reschedule_interrupt
> 2.38% [kernel] [k] __switch_to 2.62% [kernel] [k] sock_alloc_send_pskb
> 2.15% [kernel] [k] sock_alloc_send_pskb 2.52% [kernel] [k] __schedule
> 2.08% [kernel] [k] __skb_recv_datagram 2.31% [kernel] [k] try_to_wake_up
> 1.81% [kernel] [k] udp_sendmsg 2.14% [kernel] [k] system_call
> 1.76% [kernel] [k] system_call 1.98% [kernel] [k] udp_sendmsg
> 1.73% [kernel] [k] __udp4_lib_lookup 1.96% [kernel] [k] __udp4_lib_lookup
> 1.65% [kernel] [k] __slab_free.isra.42 1.78% [kernel] [k] sock_def_readable
> 1.62% [kernel] [k] try_to_wake_up 1.63% [kernel] [k] __slab_free.isra.42
> 1.43% [kernel] [k] update_rq_clock 1.60% [kernel] [k] __switch_to
> 1.43% [kernel] [k] sock_def_readable 1.52% [kernel] [k] dma_issue_pending_all
> 1.41% [kernel] [k] dma_issue_pending_all 1.48% [kernel] [k] __ip_append_data.isra.35
> 1.40% [kernel] [k] menu_select 1.44% [kernel] [k] _raw_spin_lock
> 1.36% [kernel] [k] finish_task_switch 1.38% [kernel] [k] _raw_spin_unlock_irqrestore
> 1.30% [kernel] [k] ksize 1.33% [kernel] [k] __udp4_lib_rcv
>
> Strange.
nohz=off, pipe-test with one half pinned to CPU0, the other to CPU1.
procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
TTW_QUEUE
1 0 0 3039488 50948 444720 0 0 0 0 539724 1013417 1 15 84 0 0
1 0 0 3039488 50956 444720 0 0 0 1 540853 1015679 1 15 84 0 0
1 0 0 3039364 50956 444720 0 0 0 0 541630 1017239 1 16 83 0 0
2 0 0 3038992 50956 444720 0 0 0 0 335550 1096569 4 20 76 0 0
NO_TTWU_QUEUE
1 0 0 3038992 50956 444720 0 0 0 0 33100 1318984 1 27 71 0 0
1 0 0 3038868 50956 444720 0 0 0 0 33100 1319126 2 27 71 0 0
1 0 0 3038868 50956 444720 0 0 0 0 33097 1317968 1 27 72 0 0
2 0 0 3038868 50964 444720 0 0 0 1 33104 1318558 2 27 71 0 0
We can switch faster with NO_TTWU_QUEUE, so we switch more, and that
hurts netperf UDP_STREAM throughput.. somehow. Fatter is better is not
the way context switch happy benchmarks usually work.
-Mike
next prev parent reply other threads:[~2012-10-03 13:30 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 6:51 Mel Gorman
2012-10-02 7:49 ` Mike Galbraith
2012-10-02 8:45 ` Mel Gorman
2012-10-02 9:31 ` Mike Galbraith
2012-10-02 13:14 ` Mel Gorman
2012-10-02 14:33 ` Mike Galbraith
2012-10-03 6:50 ` Mike Galbraith
2012-10-03 8:13 ` Mike Galbraith
2012-10-03 13:30 ` Mike Galbraith [this message]
2012-10-10 12:29 ` Mel Gorman
2012-10-10 13:02 ` Mike Galbraith
2012-10-10 13:05 ` Peter Zijlstra
2012-10-02 22:48 ` Rick Jones
2012-10-03 9:47 ` Mel Gorman
2012-10-03 10:22 ` Eric Dumazet
2012-10-03 18:04 ` Rick Jones
2012-10-05 9:54 ` Mel Gorman
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