Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

David Miller
2008-11-17T19:39:36Z

From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
Date: Mon, 17 Nov 2008 19:49:51 +0100

>
> * Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org> wrote:
>
> 4> The place for the sock_rfree() hit looks a bit weird, and i'll
> > investigate it now a bit more to place the real overhead point
> > properly. (i already mapped the test-bit overhead: that comes from
> > napi_disable_pending())
>
> ok, here's a new set of profiles. (again for tbench 64-thread on a
> 16-way box, with v2.6.28-rc5-19-ge14c8bf and with the kernel config i
> posted before.)

Again, do a non-NMI profile and the top (at least for me)
looks like this:

samples % app name symbol name
473 6.3928 vmlinux finish_task_switch
349 4.7169 vmlinux tcp_v4_rcv
327 4.4195 vmlinux U3copy_from_user
322 4.3519 vmlinux tl0_linux32
178 2.4057 vmlinux tcp_ack
170 2.2976 vmlinux tcp_sendmsg
167 2.2571 vmlinux U3copy_to_user

That tcp_v4_rcv() hit is %98 on the wake_up() call it does.