From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Wagner <daniel.wagner@bmw-carit.de>
Subject: Re: [RFC v1 0/5] fs/locks: Use plain percpu spinlocks instead of
 lglock to protect file_lock
Date: Tue, 24 Feb 2015 16:58:26 +0100
Message-ID: <54EC9FA2.1030000@bmw-carit.de>
References: <1424443195-18676-1-git-send-email-daniel.wagner@bmw-carit.de> <87vbiwwotb.fsf@tassilo.jf.intel.com>
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Cc: Jeff Layton <jlayton@poochiereds.net>,
	<linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	John Kacur <jkacur@redhat.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"J. Bruce Fields" <bfields@fieldses.org>
To: Andi Kleen <andi@firstfloor.org>
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In-Reply-To: <87vbiwwotb.fsf@tassilo.jf.intel.com>
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On 02/20/2015 05:05 PM, Andi Kleen wrote:
> Daniel Wagner <daniel.wagner@bmw-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