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From: Andrew Morton <akpm@zip.com.au>
To: Robert Love <rml@tech9.net>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] low-latency zap_page_range()
Date: Thu, 29 Aug 2002 14:22:12 -0700	[thread overview]
Message-ID: <3D6E9084.820B2608@zip.com.au> (raw)
In-Reply-To: 1030655532.12110.2691.camel@phantasy

Robert Love wrote:
> 
> On Thu, 2002-08-29 at 17:00, Andrew Morton wrote:
> 
> > That's an interesting point.  page_table_lock is one of those locks
> > which is occasionally held for ages, and frequently held for a short
> > time.
> 
> Since latency is a direct function of lock held times in the preemptible
> kernel, and I am seeing disgusting zap_page_range() latencies, the lock
> is held a long time.
> 
> So we know it is held forever and a day... but is there contention?

I'm sure there is, but nobody has measured the right workload.

Two CLONE_MM threads, one running mmap()/munmap(), the other trying
to fault in some pages.  I'm sure someone has some vital application
which does exactly this.  They always do :(

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@zip.com.au>
To: Robert Love <rml@tech9.net>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] low-latency zap_page_range()
Date: Thu, 29 Aug 2002 14:22:12 -0700	[thread overview]
Message-ID: <3D6E9084.820B2608@zip.com.au> (raw)
In-Reply-To: 1030655532.12110.2691.camel@phantasy

Robert Love wrote:
> 
> On Thu, 2002-08-29 at 17:00, Andrew Morton wrote:
> 
> > That's an interesting point.  page_table_lock is one of those locks
> > which is occasionally held for ages, and frequently held for a short
> > time.
> 
> Since latency is a direct function of lock held times in the preemptible
> kernel, and I am seeing disgusting zap_page_range() latencies, the lock
> is held a long time.
> 
> So we know it is held forever and a day... but is there contention?

I'm sure there is, but nobody has measured the right workload.

Two CLONE_MM threads, one running mmap()/munmap(), the other trying
to fault in some pages.  I'm sure someone has some vital application
which does exactly this.  They always do :(
--
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  reply	other threads:[~2002-08-29 21:19 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-08-29 15:31 [PATCH] low-latency zap_page_range() Robert Love
2002-08-29 15:31 ` Robert Love
2002-08-29 20:30 ` Andrew Morton
2002-08-29 20:30   ` Andrew Morton
2002-08-29 20:40   ` Robert Love
2002-08-29 20:40     ` Robert Love
2002-08-29 20:46     ` Robert Love
2002-08-29 20:46       ` Robert Love
2002-08-29 20:59     ` Andrew Morton
2002-08-29 20:59       ` Andrew Morton
2002-08-29 21:38       ` William Lee Irwin III
2002-08-29 21:38         ` William Lee Irwin III
2002-08-29 22:37         ` Linus Torvalds
2002-08-29 23:06           ` William Lee Irwin III
2002-08-29 21:00     ` Andrew Morton
2002-08-29 21:00       ` Andrew Morton
2002-08-29 21:12       ` Robert Love
2002-08-29 21:12         ` Robert Love
2002-08-29 21:22         ` Andrew Morton [this message]
2002-08-29 21:22           ` Andrew Morton
2002-08-29 21:46           ` Rik van Riel
2002-08-29 21:46             ` Rik van Riel

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