linux-kernel - Re: [RFC 1/1] mm: Add per-task struct tlb counters

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Date:   Thu, 15 Sep 2022 10:50:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Joe Damato <jdamato@...tly.com>
Cc:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-mm@...ck.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC 1/1] mm: Add per-task struct tlb counters

On Wed, Sep 14, 2022 at 07:15:08AM -0700, Joe Damato wrote:

> I could patch count_vm_tlb... to account on a per-task basis. That seems
> reasonable to me... assuming you and others are convinced that it's a
> better approach than tracepoints ;)

Well, we *could* do a lot of things, but we can all spend out cycles
only once. Doing endless variations of statistics contributes to
death-by-a-thoudsand-cuts.

If you really think you need this, write yourself an eBPF program and
attach it to these tracepoints. Then you get less cycles for useful
work, but the rest of us isn't bothered by that.