From: Benjamin LaHaise <bcrl@kvack.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@osdl.org>,
sekharan@us.ibm.com,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Avoid calling down_read and down_write during startup
Date: Fri, 24 Feb 2006 10:15:10 -0500 [thread overview]
Message-ID: <20060224151510.GC7101@kvack.org> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0602241003450.5071-100000@iolanthe.rowland.org>
On Fri, Feb 24, 2006 at 10:04:23AM -0500, Alan Stern wrote:
> What do you think of the two suggestions in my previous message?
Even if the read version of the lock only touches a cacheline local to
the cpu, you'd still have to use the lock prefix to allow for correctness
when a writer comes along. It is not cacheline bouncing that worries me,
it is serialising instructions and memory barriers as those hurt immensely
when the data is in the cache. I've been looking at a lot of profiles on
P4s of late, and every single locked instruction is painful as it means
all of the memory ordering rules come into play. Neither suggestion
addresses that overhead that has been introduced.
-ben
--
"Ladies and gentlemen, I'm sorry to interrupt, but the police are here
and they've asked us to stop the party." Don't Email: <dont@kvack.org>.
next prev parent reply other threads:[~2006-02-24 15:20 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-21 15:54 [PATCH] Register atomic_notifiers in atomic context Alan Stern
2006-02-21 23:28 ` Andrew Morton
2006-02-22 16:08 ` Alan Stern
2006-02-22 16:12 ` Randy.Dunlap
2006-02-23 2:26 ` Andrew Morton
2006-02-23 17:15 ` Alan Stern
2006-02-23 19:03 ` Andrew Morton
2006-02-23 22:28 ` [PATCH] The idle notifier chain should be atomic Alan Stern
2006-02-23 23:49 ` Andi Kleen
2006-02-24 3:24 ` Alan Stern
2006-02-24 3:27 ` Andi Kleen
2006-02-24 4:04 ` Alan Stern
2006-02-23 22:36 ` [PATCH] Avoid calling down_read and down_write during startup Alan Stern
2006-02-23 22:37 ` Benjamin LaHaise
2006-02-24 0:16 ` Andrew Morton
2006-02-24 3:18 ` Alan Stern
2006-02-24 14:40 ` Benjamin LaHaise
2006-02-24 15:04 ` Alan Stern
2006-02-24 15:15 ` Benjamin LaHaise [this message]
2006-02-24 16:44 ` Alan Stern
2006-02-24 16:44 ` Benjamin LaHaise
2006-02-24 17:59 ` Alan Stern
2006-02-24 18:37 ` Benjamin LaHaise
2006-02-24 20:21 ` Alan Stern
2006-02-24 14:39 ` Benjamin LaHaise
2006-02-24 15:03 ` Alan Stern
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