From: Eric Dumazet <eric.dumazet@gmail.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Matthew Wilcox <matthew@wil.cx>,
Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Prevent users from disabling tickless
Date: Sun, 02 Jan 2011 10:15:42 +0100 [thread overview]
Message-ID: <1293959742.2535.73.camel@edumazet-laptop> (raw)
In-Reply-To: <20110102085755.GA32469@atrey.karlin.mff.cuni.cz>
Le dimanche 02 janvier 2011 à 09:57 +0100, Pavel Machek a écrit :
> Hi!
>
> > Disabling NO_HZ has a serious negative effect on performance -- an extra
> > 70us per I/O. Prevent users from deselecting it.
> >
> > Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>
> System with fixed HZ is really simpler etc... and 70us per i/o does
> not sound that bad.
>
> Anyway, should not i/o overhead just be fixed?
Also, where are those 70us spent exactly ? Once per clock tick ?
For me, I/O can be an ethernet frame sent or received, and I never
noticed such a delay.
At least, commit message sounds very evasive too me.
next prev parent reply other threads:[~2011-01-02 9:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-21 23:39 Matthew Wilcox
2010-12-21 23:46 ` Rafael J. Wysocki
2010-12-22 0:24 ` Matthew Wilcox
2010-12-22 0:38 ` Rafael J. Wysocki
2010-12-22 21:00 ` Frank Rowand
2010-12-22 21:34 ` Matthew Wilcox
2010-12-22 22:32 ` Frank Rowand
2010-12-26 22:22 ` Len Brown
2010-12-26 23:20 ` Grant Coady
2010-12-26 23:23 ` Regarding kernel work queue issues Raj Kumar
2010-12-25 15:42 ` [PATCH] Prevent users from disabling tickless Stefan Richter
2011-01-02 8:57 ` Pavel Machek
2011-01-02 9:15 ` Eric Dumazet [this message]
2011-01-02 10:59 ` Serge Belyshev
2011-01-02 11:06 ` Remy Bohmer
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