linux-kernel - Re: [RFC v1 0/5] fs/locks: Use plain percpu spinlocks instead of lglock to protect file

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Date:	Tue, 24 Feb 2015 16:58:26 +0100
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Jeff Layton <jlayton@...chiereds.net>,
	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	John Kacur <jkacur@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"J. Bruce Fields" <bfields@...ldses.org>
Subject: Re: [RFC v1 0/5] fs/locks: Use plain percpu spinlocks instead of
 lglock to protect file_lock

On 02/20/2015 05:05 PM, Andi Kleen wrote:
> Daniel Wagner <daniel.wagner@...-carit.de> writes:
>>
>> I am looking at how to get rid of lglock. Reason being -rt is not too
>> happy with that lock, especially that it uses arch_spinlock_t and
> 
> AFAIK it could just use normal spinlock. Have you tried that?

I have tried it. At least fs/locks.c didn't blow up. The benchmark
results (lockperf) indicated that using normal spinlocks is even
slightly faster. Simply converting felt like cheating. It might be
necessary for the other user (kernel/stop_machine.c). Currently it looks
like there is some additional benefit getting lglock away in fs/locks.c.

cheers,
daniel
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