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From: P@draigBrady.com
To: Andrea Arcangeli <andrea@novell.com>
Cc: netdev@oss.sgi.com, Ingo Molnar <mingo@elte.hu>
Subject: Re: gettimeofday scalability
Date: Tue, 05 Oct 2004 20:16:33 +0100	[thread overview]
Message-ID: <4162F311.4050009@draigBrady.com> (raw)
In-Reply-To: <20041005185553.GG26820@dualathlon.random>

Andrea Arcangeli wrote:
> On Tue, Oct 05, 2004 at 05:36:06PM +0100, P@draigBrady.com wrote:
> 
>>So can anyone summarise the relative merits of these locking
>>mechanisms, before I start benchmarking?
> 
> 
> frlock/seqlock (2.4/2.6 respectively) is the way to go, no write
> starvation, and zero cacheline bouncing. 

Cheers.

Perhaps the confusing comment wrt brlock at the
top of seqlock.h can be changed so?

> upgrade to x86-64, there I implemented gettimeofday with vsyscalls which
> also avoids entering exiting userspace which becomes the by far biggest
> overhead after using seqlock. (speedup is tenfold or so)

This is all in kernel space.
However Stephen's suggestion of reading the tsc in user space
may be a runner, as I just care about relative times.

thanks guys!

Pádraig.

  reply	other threads:[~2004-10-05 19:16 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-10-05 16:36 gettimeofday scalability P
2004-10-05 18:35 ` David S. Miller
2004-10-05 18:48 ` Stephen Hemminger
2004-10-05 18:55 ` Andrea Arcangeli
2004-10-05 19:16   ` P [this message]
2004-10-05 19:35     ` Andrea Arcangeli
2004-10-05 19:18 ` Ingo Molnar

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