Hi,

On 06/27/2013 06:54 PM, Maxime Ripard wrote:

On Thu, Jun 27, 2013 at 11:54:11AM +0200, Hans de Goede wrote:

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Hi,

On 06/27/2013 11:43 AM, Maxime Ripard wrote:

quoted

On Thu, Jun 27, 2013 at 11:27:02AM +0200, Hans de Goede wrote:

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Hi,

On 06/26/2013 11:16 PM, Maxime Ripard wrote:

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Hi everyone,

<snip>

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It also finally adds a clocksource from the free running counter found in the
A10/A13 SoCs.

Hmm, have you benchmarked this? There have been reports from linux-sunxi kernel
users (xbmc project) that the waiting for the latch is quite slow. Note we
don't have anything better yet in the linux-sunxi kernel.

No. I didn't.

Do you have any pointers to these discussions?

The original discussion should be somewhere here:
https://groups.google.com/forum/#!forum/linux-sunxi

But I could not find it (it is probably hidden under
an unlogical subject).

I searched a bit and it seems to be that discussion:
https://groups.google.com/d/msg/linux-sunxi/gaTDngPT7Is/oeLtWb1N1wIJ

quoted

Looking at my own notes (a small TODO file), I've
written down that the reporter reports:

  -current clocksource can cause us to run with interrupts disabled for 17%
   of the time, see "perf top" output

This is with a workload which does a lot of gettimeofday
calls.

Siarhei however notes that even higher-end SoCs like the exynos5 have
similar performances with that regard. So I'm not sure we can do
something about it, except what is suggested in the above mail, which
looks rather unsafe.

Anyway, like you said, we have no easy other solution, and we lacked
such support until now.

So why not merge this code for now, and try to optimise it later if we
find it's needed.

That is fine with me, I just wanted to share that this has shown as
a bottleneck in some benchmarks in case anyone has a clever idea to
fix it ...

Regards,

Hans