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SubjectRe: sched: context tracking demolishes pipe-test
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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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