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Re: [RFC] Dynamic lock elision support
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: "Paul E. Murphy" <murphyp at linux dot vnet dot ibm dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Tue, 18 Aug 2015 13:46:23 -0300
- Subject: Re: [RFC] Dynamic lock elision support
- Authentication-results: sourceware.org; auth=none
- References: <55D358D8 dot 7020303 at linux dot vnet dot ibm dot com>
Andi Kleen has sent some patches to add tunables for lock elision with
But he has not yet ping or followed up with these. I also would prefer
to add tunable to be as platform agnostic as possible, since we have
3 architectures that support LE (x86, ppc, zarch). So I would suggest
you work on this options and/or adjust the patch on these.
Also, we may want to avoid a configure flag and enable LE support as
default for powerpc, but disable as default (enabled through env. vars
as Andi Kleen patchset).
On 18-08-2015 13:10, Paul E. Murphy wrote:
> Elided locks can have mixed overall performance in practice. That is, there is some non-trivial tuning a user might have to do to see the positive benefits. Additionally, when tuning the adaptive lock constants on PPC, my experimentation seems to correlate tuned values with both the number of hardware threads per core, and the behavior of the application.
> My initial thought is elision should be disabled by default, with an environment variable to toggle both support, and potentially override tuning constants.