linux-kernel - Re: [RFC PATCH] wfcqueue: implement __wfcq_enqueue

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Date:	Mon, 8 Apr 2013 02:17:50 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>
Subject: Re: [RFC PATCH] wfcqueue: implement __wfcq_enqueue_head() (v3)

Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> Changes since v2:
> * Only issue cmpxchg() if queue was empty.
> * Add missing memory barrier.

Thanks!

There's a slight drop in performance either from the barrier or larger
code, but I'm not worried (it was around 9-10s before wfcqueue).

$ time ./eponeshotmt -c 1000000 -w 4 -t 4 -f 10
real    0m 5.83s
user    0m 1.35s
sys     0m 21.95s

I also ran v2 on Davide Libenzi's totalmess epoll stresser for a few
hours yesterday without failures.  Running totalmess right now on v3,
so far so good :)

Tested-by: Eric Wong <normalperson@...t.net>
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