From: Stanislav Meduna <stano@meduna.org>
To: linux-rt-users@vger.kernel.org
Subject: Re: loading pages to memory causes high latency
Date: Sat, 27 Oct 2012 11:06:26 +0200 [thread overview]
Message-ID: <508BA412.5020708@meduna.org> (raw)
In-Reply-To: <alpine.LFD.2.02.1210271029370.2756@ionos>
On 27.10.2012 10:38, Thomas Gleixner wrote:
> There is not much we can do about that unless we want to do a major
> surgery on that pata driver code.
>
> So either you disable the throttler or you reconfigure the pata irq
> thread to SCHED_OTHER, which will slow it down a bit, but avoids the
> hogging of the machine with a RT task going wild.
Thank you for the analysis. Yep I'll reconfigure it to SCHED_OTHER -
file access is a totally low-prio thing in my application and I was more
afraid of a possibility where someone fetching logfiles or something
like that will bring the application to the knees.
BTW what granularity does the throttler have? I cannot live with
50 ms lag once in a second, but in my case I can well live with
5 ms lag once in 100 ms (even if that means that the throttler
would be activated more often).
Right now I have
CONFIG_TICK_ONESHOT=y
CONFIG_NO_HZ=y
CONFIG_HZ=1000
CONFIG_SCHED_HRTICK=y
and lacking better choices my clock source is TSC. I admit that
I do not know what precisely each setting does - the NO_HZ combined
with HZ=1000 looks a bit weird ;)
Best regards
--
Stano
next prev parent reply other threads:[~2012-10-27 9:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 18:00 loading pages to memory causes high latency Stanislav Meduna
2012-10-26 21:04 ` Thomas Gleixner
2012-10-27 8:38 ` Thomas Gleixner
2012-10-27 9:06 ` Stanislav Meduna [this message]
2012-10-27 9:56 ` Thomas Gleixner
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