Re: sched: context tracking demolishes pipe-test
From: Mike Galbraith
Date: Tue Jul 02 2013 - 03:20:14 EST
CCs net-wizards since staring at profile/annotation isn't helping, and I
know all too well how these things laugh perversely at bisection.
On Tue, 2013-07-02 at 06:03 +0200, Mike Galbraith wrote:
> On Mon, 2013-07-01 at 11:20 +0200, Mike Galbraith wrote:
> > On Mon, 2013-07-01 at 11:12 +0200, Mike Galbraith wrote:
> > > On Mon, 2013-07-01 at 10:06 +0200, Peter Zijlstra wrote:
> > >
> > > > So aside from the context tracking stuff, there's still a regression
> > > > we might want to look at. That's still a ~10% drop against 2.6.32 for
> > > > TCP_RR and few percents for tbench.
> > >
> > > Yeah, known, and some of it's ours.
> >
> > (btw tbench has a ~5% phase-of-moon jitter, you can pretty much
> > disregard that one)
>
> Hm. Seems we don't own much of TCP_RR regression after all, somewhere
> along the line while my silly-tester hat was moldering, we got some
> cycles back.. in the light config case anyway.
>
> With wakeup granularity set to zero, per pipe-test, scheduler is within
> variance of .32, sometimes appearing a tad lighter, though usually a wee
> bit heavier. TCP_RR throughput delta does not correlate.
>
> echo 0 > sched_wakeup_granularity_ns
>
> pipe-test
> 2.6.32-regress 689.8 Khz 1.000
> 3.10.0-regress 682.5 Khz .989
>
> netperf TCP_RR
> 2.6.32-regress 117910.11 Trans/sec 1.000
> 3.10.0-regress 96955.12 Trans/sec .822
>
> It should be closer than this.
>
> 3.10.0-regress 2.6.32-regress
> 3.85% [kernel] [k] tcp_ack 4.04% [kernel] [k] tcp_sendmsg
> 3.34% [kernel] [k] __schedule 3.63% [kernel] [k] schedule
> 2.93% [kernel] [k] tcp_sendmsg 2.86% [kernel] [k] tcp_recvmsg
> 2.54% [kernel] [k] tcp_rcv_established 2.83% [kernel] [k] tcp_ack
> 2.26% [kernel] [k] tcp_transmit_skb 2.19% [kernel] [k] system_call
> 1.90% [kernel] [k] __netif_receive_skb_core 2.16% [kernel] [k] tcp_transmit_skb
> 1.87% [kernel] [k] tcp_v4_rcv 2.07% libc-2.14.1.so [.] __libc_recv
> 1.84% [kernel] [k] tcp_write_xmit 1.95% [kernel] [k] _spin_lock_bh
> 1.70% [kernel] [k] __switch_to 1.89% libc-2.14.1.so [.] __libc_send
> 1.57% [kernel] [k] tcp_recvmsg 1.77% [kernel] [k] tcp_rcv_established
> 1.54% [kernel] [k] _raw_spin_lock_bh 1.70% [kernel] [k] netif_receive_skb
> 1.52% libc-2.14.1.so [.] __libc_recv 1.61% [kernel] [k] tcp_v4_rcv
> 1.43% [kernel] [k] ip_rcv 1.49% [kernel] [k] native_sched_clock
> 1.35% [kernel] [k] local_bh_enable 1.49% [kernel] [k] tcp_write_xmit
> 1.33% [kernel] [k] _raw_spin_lock_irqsave 1.46% [kernel] [k] __switch_to
> 1.26% [kernel] [k] ip_queue_xmit 1.35% [kernel] [k] dev_queue_xmit
> 1.16% [kernel] [k] __inet_lookup_established 1.29% [kernel] [k] __alloc_skb
> 1.14% [kernel] [k] mod_timer 1.27% [kernel] [k] skb_release_data
> 1.13% [kernel] [k] process_backlog 1.26% netserver [.] recv_tcp_rr
> 1.13% [kernel] [k] read_tsc 1.22% [kernel] [k] local_bh_enable
> 1.13% libc-2.14.1.so [.] __libc_send 1.18% netperf [.] send_tcp_rr
> 1.12% [kernel] [k] system_call 1.18% [kernel] [k] sched_clock_local
> 1.07% [kernel] [k] tcp_event_data_recv 1.11% [kernel] [k] copy_user_generic_string
> 1.04% [kernel] [k] ip_finish_output 1.07% [kernel] [k] _spin_lock_irqsave
>
> -Mike
>
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