From: Ingo Molnar <mingo@elte.hu>
To: Nivedita Singhvi <niv@us.ibm.com>
Cc: Dave Sperry <dave_sperry@ieee.org>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
netdev <netdev@vger.kernel.org>
Subject: Re: Poor UDP performance using 2.6.21-rc5-rt5
Date: Mon, 2 Apr 2007 08:30:18 +0200 [thread overview]
Message-ID: <20070402063018.GA10209@elte.hu> (raw)
In-Reply-To: <20070402055509.GC3284@elte.hu>
* Ingo Molnar <mingo@elte.hu> wrote:
> one thing to check would be whether both kernels use the same
> clocksource, via:
>
> cat /sys/devices/system/clocksource/clocksource0/current_clocksource
>
> but at first sight there's no clocksource related overhead in the
> oprofile.
i've started a similar netperf test and clocksource overhead dominates
the profile:
5553 handle_fasteoi_irq 26.1934
5940 nv_start_xmit_optimized 6.6892
6014 ack_ioapic_quirk_irq 44.5481
7591 mask_IO_APIC_irq 154.9184
8155 __copy_from_user_ll 37.4083
13371 io_apic_base 417.8438
13565 get_next_timer_interrupt 29.7478
13966 __modify_IO_APIC_irq 151.8043
14213 do_irqd 22.7045
17834 unmask_IO_APIC_irq 424.6190
20503 __schedule 6.4455
48456 cpu_idle 180.8060
170001 acpi_pm_read 8947.4211
517107 total 0.1566
acpi_pm_read() amounts to 32% overhead!
i'm not sure why the oprofile results show no clocksource overhead - the
-rt kernel typically uses the pm-timer on Opterons.
to get more comparable results, boot the vanilla kernel with the
"apicpmtimer" boot option, and/or do this after bootup:
echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
Ingo
prev parent reply other threads:[~2007-04-02 6:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <461004CE.1030009@ieee.org>
2007-04-01 20:07 ` Poor UDP performance using 2.6.21-rc5-rt5 Nivedita Singhvi
2007-04-01 22:00 ` Dave Sperry
2007-04-02 5:55 ` Ingo Molnar
2007-04-02 6:30 ` Ingo Molnar [this message]
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