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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 5 Jun 2019 13:16:46 -0700
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Subject: Re: [PATCH] lockref: Limit number of cmpxchg loop retries
To:     Jan Glauber <jglauber@cavium.com>
Cc:     Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Jayachandran Chandrasekharan Nair <jnair@marvell.com>,
        Jan Glauber <jglauber@marvell.com>
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On Wed, Jun 5, 2019 at 6:49 AM Jan Glauber <jglauber@cavium.com> wrote:
>
> Add an upper bound to the loop to force the fallback to spinlocks
> after some time. A retry value of 100 should not impact any hardware
> that does not have this issue.
>
> With the retry limit the performance of an open-close testcase
> improved between 60-70% on ThunderX2.

Btw, did you do any kind of performance analysis across different
retry limit values?

I'm perfectly happy to just pick a random number and '100' looks fine
to me, so this is mainly out of curiosity.

                       Linus