From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <npiggin@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
hpa@zytor.com, jeremy@xensource.com, chrisw@sous-sol.org,
zach@vmware.com, rusty@rustcorp.com.au
Subject: Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT
Date: Thu, 22 Jan 2009 14:26:44 -0800 [thread overview]
Message-ID: <4978F2A4.8010807@goop.org> (raw)
In-Reply-To: <20090120112634.GA20858@elte.hu>
Ingo Molnar wrote:
> Ouch, that looks unacceptably expensive. All the major distros turn
> CONFIG_PARAVIRT on. paravirt_ops was introduced in x86 with the express
> promise to have no measurable runtime overhead.
>
> ( And i suspect the real life mmap cost is probably even more expensive,
> as on a Barcelona all of lmbench fits into the cache hence we dont see
> any real $cache overhead. )
>
> Jeremy, any ideas where this slowdown comes from and how it could be
> fixed?
>
I just posted a couple of patches to pick some low-hanging fruit. It
turns out that we don't need to do any pvops calls to do pte flag
manipulations. I'd be interested to see how much of a difference it
makes (it reduces the static code size by a few k).
J
next prev parent reply other threads:[~2009-01-22 22:27 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-20 11:05 lmbench lat_mmap slowdown with CONFIG_PARAVIRT Nick Piggin
2009-01-20 11:26 ` Ingo Molnar
2009-01-20 12:34 ` Nick Piggin
2009-01-20 12:45 ` Ingo Molnar
2009-01-20 13:41 ` Nick Piggin
2009-01-20 14:03 ` Ingo Molnar
2009-01-20 14:14 ` Nick Piggin
2009-01-20 14:17 ` Ingo Molnar
2009-01-20 14:41 ` Nick Piggin
2009-01-20 15:00 ` Ingo Molnar
2009-01-20 15:13 ` Ingo Molnar
2009-01-20 19:37 ` Ingo Molnar
2009-01-20 20:45 ` Jeremy Fitzhardinge
2009-01-20 20:56 ` Ingo Molnar
2009-01-21 7:27 ` Nick Piggin
2009-01-21 22:23 ` Jeremy Fitzhardinge
2009-01-22 22:28 ` Zachary Amsden
2009-01-22 22:44 ` Jeremy Fitzhardinge
2009-01-22 22:49 ` H. Peter Anvin
2009-01-22 22:58 ` Zachary Amsden
2009-01-22 23:52 ` H. Peter Anvin
2009-01-23 0:08 ` Jeremy Fitzhardinge
2009-01-22 22:55 ` Zachary Amsden
2009-01-23 0:14 ` Jeremy Fitzhardinge
2009-01-27 7:59 ` Ingo Molnar
2009-01-27 8:24 ` Jeremy Fitzhardinge
2009-01-27 10:17 ` Jeremy Fitzhardinge
2009-01-20 19:05 ` Zachary Amsden
2009-01-20 19:31 ` Ingo Molnar
2009-01-22 22:26 ` Jeremy Fitzhardinge [this message]
2009-01-22 23:04 ` Ingo Molnar
2009-01-22 23:30 ` Zachary Amsden
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