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From: "David S. Miller" <davem@redhat.com>
To: dipankar@in.ibm.com
Cc: wli@holomorphy.com, akpm@digeo.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: 2.5.69-mm1
Date: Tue, 06 May 2003 07:20:51 -0700 (PDT)	[thread overview]
Message-ID: <20030506.072051.45141886.davem@redhat.com> (raw)
In-Reply-To: <20030506152555.GC9875@in.ibm.com>

   From: Dipankar Sarma <dipankar@in.ibm.com>
   Date: Tue, 6 May 2003 20:55:55 +0530

   On Tue, May 06, 2003 at 05:02:22AM -0700, David S. Miller wrote:
   > rwlocks believe it or not tend not to be superior over spinlocks,
   > they actually promote cache line thrashing in the case they
   > are actually being effective (>1 parallel reader)
   
   Provided there isn't a very heavy contention among readers for the
   spin_lock.

Even if there are thousands of readers trying to get the lock
at the same time, unless your hold time is significant these
readers will merely thrash the cache getting the rwlock_t.
And then thrash it again to release the rwlock_t.

This is especially true if the spinlock lives in the same cache
lines as the data it protects.

All of this is magnified on NUMA.

  reply	other threads:[~2003-05-06 15:16 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-05-05  6:16 2.5.69-mm1 Andrew Morton
2003-05-05 15:32 ` 2.5.69-mm1 Andrei Ivanov
2003-05-05 16:45   ` 2.5.69-mm1 Greg KH
2003-05-06  9:49     ` 2.5.69-mm1 Andrei Ivanov
2003-05-05 18:44   ` 2.5.69-mm1 Andrew Morton
2003-05-05 21:01 ` 2.5.69-mm1 William Lee Irwin III
2003-05-06 11:09   ` 2.5.69-mm1 Dipankar Sarma
2003-05-06 12:02     ` 2.5.69-mm1 David S. Miller
2003-05-06 15:25       ` 2.5.69-mm1 Dipankar Sarma
2003-05-06 14:20         ` David S. Miller [this message]
2003-05-06 15:47           ` 2.5.69-mm1 Dipankar Sarma
2003-05-05 21:02 ` 2.5.69-mm1 William Lee Irwin III
2003-05-06 14:33 ` 2.5.69-mm1 Steven Cole
2003-05-06 15:33   ` 2.5.69-mm1 Andrew Morton
2003-05-06 15:36     ` 2.5.69-mm1 Eric W. Biederman
2003-05-06 16:35       ` 2.5.69-mm1 Steven Cole

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