linux-kernel - Re: [RFC PATCH 3/8] perf: Init/fini PMU specific data

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Date:   Mon, 2 Dec 2019 17:43:13 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Andi Kleen <ak@...ux.intel.com>, kan.liang@...ux.intel.com,
        mingo@...hat.com, acme@...nel.org, tglx@...utronix.de,
        bp@...en8.de, linux-kernel@...r.kernel.org, eranian@...gle.com,
        vitaly.slobodskoy@...el.com
Subject: Re: [RFC PATCH 3/8] perf: Init/fini PMU specific data

On Mon, Dec 02, 2019 at 07:38:00PM +0300, Alexey Budankov wrote:
> 
> On 02.12.2019 17:59, Andi Kleen wrote:
> >>
> >> This is atricous crap. Also it is completely broken for -RT.
> > 
> > Well can you please suggest how you would implement it instead?
> 
> FWIW,
> An alternative could probably be to make task_ctx_data allocations
> on the nearest context switch in, and obvious drawback is slowdown on
> this critical path, but it could be amortized by static branches.

Context switch is under a raw_spinlock_t too.