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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        andrea.parri@amarulasolutions.com,
        Will Deacon <will.deacon@arm.com>,
        Akira Yokosawa <akiyks@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        David Howells <dhowells@redhat.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        Nick Piggin <npiggin@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] tools/memory-model: Add extra ordering for locks and remove it for ordinary release/acquire
In-Reply-To: <87601fz1kc.fsf@concordia.ellerman.id.au>
References: <20180712134821.GT2494@hirez.programming.kicks-ass.net> <Pine.LNX.4.44L0.1807121236470.1306-100000@iolanthe.rowland.org> <20180712172838.GU3593@linux.vnet.ibm.com> <20180712180511.GP2476@hirez.programming.kicks-ass.net> <CA+55aFxwez8zSa2f2GpcaAkFX27Vt-s0nWdd0mZ6yGM8ipCR0A@mail.gmail.com> <20180713110851.GY2494@hirez.programming.kicks-ass.net> <87tvp3xonl.fsf@concordia.ellerman.id.au> <20180713164239.GZ2494@hirez.programming.kicks-ass.net> <87601fz1kc.fsf@concordia.ellerman.id.au>
Date:   Wed, 18 Jul 2018 23:16:25 +1000
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Michael Ellerman <mpe@ellerman.id.au> writes:
> Peter Zijlstra <peterz@infradead.org> writes:
...
>
> I'll do some kernbench runs tomorrow and see if it shows up there.

Finally got some numbers.

The summary is it's in the noise, the average delta is +0.1s (total time
is ~67s, so 0.17%) but the standard deviation is ~0.2s.

So that's probably a real slow down, but it's very minor.

I guess that's not surprising, given kernbench should be spending the
bulk of its time in userspace.

cheers