linux-kernel - Re: [PATCH 00/36] cputime: Convert core use of cputime

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Date:   Mon, 21 Nov 2016 17:22:20 +0100
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Mackerras <paulus@...ba.org>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>
Subject: Re: [PATCH 00/36] cputime: Convert core use of cputime_t to nsecs

On Mon, Nov 21, 2016 at 10:49:23AM +0100, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > > But I am still not happy about the approach. What is the compelling reason for 
> > > this change except for the "but it looks ugly"?
> > 
> > The diffstat (600 lines removed). Also the fact that we have all these 
> > workarounds in the core code just for the special case of 1 arch (s390) and a 
> > half (powerpc with CONFIG_VIRT_CPU_ACCOUNTING_NATIVE).
> > 
> > I'd much rather have all that complexity moved in a vtime_native.c shared by 
> > s390 and powerpc that takes care of proper accumulation in cputime_t and flushes 
> > that on ticks in nsecs rather than having all these cputime_t game all over the 
> > kernel.
> 
> I agree - we really want to concentrate complexity in such a fashion and generally 
> standardize on nanosecs, and the diffstat of the patchset is really nice.

Yeah, although the diffstat might become less impressive after the accumulator code,
but still worth it I think.

> The patchset obviously has to build (and work!) on s390/powerpc properly.

Of course!

Thanks.