linux-kernel - Re: perf: multiple mmap of fd behavior on x86/ARM

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Date:   Fri, 11 Aug 2017 18:09:21 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Vince Weaver <vincent.weaver@...ne.edu>
Cc:     linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: perf: multiple mmap of fd behavior on x86/ARM

On Fri, Aug 11, 2017 at 12:51:12PM -0400, Vince Weaver wrote:
> On Fri, 11 Aug 2017, Mark Rutland wrote:
> > Just to check, how does x86 behave on each of those kernel releases?
> > 
> > Many things have changed since v4.4.
> 
> I'm fairly sure this test (well, the equivelent code in 
> tests/record_sample/record_mmap that I based the test on) has been passing 
> on all of my x86 test machines since ~3.10 or so, or else I would noticed.

Ok.

> If I can get a custom kernel to boot on one of my machines I can start 
> digging in and see if I can find where the EINVAL comes from.

>From a quick scan, I can't spot anything obvious that would affect the
arm64 perf mmap behaviour, that has changed since v4.9.

> This isn't some key thing that needs to be fixed, I was just curious about 
> the behavior difference between x86 and ARM. 

Sure; likewise I'm curious.

Thanks,
Mark.