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Re: [RFC] Dynamic lock elision support
- From: Andi Kleen <andi at firstfloor dot org>
- To: Steven Munroe <munroesj at linux dot vnet dot ibm dot com>
- Cc: "Paul E. Murphy" <murphyp at linux dot vnet dot ibm dot com>, Carlos O'Donell <carlos at redhat dot com>, Siddhesh Poyarekar <siddhesh at redhat dot com>, Andi Kleen <andi at firstfloor dot org>, Stefan Liebler <stli at linux dot vnet dot ibm dot com>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Wed, 2 Sep 2015 02:52:24 +0200
- 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> <55D3615F dot 1020300 at linaro dot org> <55D3AA72 dot 7000901 at linux dot vnet dot ibm dot com> <1440797277 dot 11285 dot 8 dot camel at oc7878010663>
On Fri, Aug 28, 2015 at 04:27:57PM -0500, Steven Munroe wrote:
> On Tue, 2015-08-18 at 16:58 -0500, Paul E. Murphy wrote:
> > Was any consensus reached regarding adding environment variables for
> > tuneables? The only alternative I've seen floated is to use HWCAP bits to
> > point to a separate variant of libpthread. It seemed more undesirable.
> >
> > I like Andi's approach, and am willing to rework and resubmit Andi's
> > patchset for the remaining archs if there is agreement with his approach.
> >
> > I think we would all benefit from a runtime mechanism to transition
> > into TLE while we work to best utilize this new tool.
> >
> How do we move this forward and who needs to be brought into the
> consensus?
Hi Steven,
I posted the patch a few times, but noone reviewed it. I guess it mainly
needs reviewers.
Yes tuning ability is very important for elision.
When the tuning was originally discussed Roland didn't like it. However
I later discussed it with him privately and I addressed all his
points (by adding a white list) for the environment tuning.
That was implemented in my latest patchkits.
There was unfortunately no consensus on a real run time tuning
capability for the program (other than turning it off by changing
the mutex type). I know some people do it by patching the mutex
structures though.
BTW I also have a hack to patch it through LD_PRELOAD, but yes
an official interface would be better.
-Andi