Re: [PATCH v9 00/13] support "task_isolation" mode for nohz_full

[Chris Metcalf]

(Adding Mark to cc's)

On 01/12/2016 05:07 AM, Will Deacon wrote:
> On Mon, Jan 11, 2016 at 04:15:50PM -0500, Chris Metcalf wrote:
> > Ping!  There has been no substantive feedback to this version of
> > the patch in the week since I posted it, which optimistically suggests
> > to me that people may be satisfied with it.  If that's true, Frederic,
> > I assume this would be pulled into your tree?
> >
> > I have slightly updated the v9 patch series since this posting:
> >
> > [...]
> >
> > - Incorporated Mark Rutland's changes to convert arm64
> >    assembly to C code instead of using my own version.
> Please avoid queuing these patches -- the first is already in the arm64
> queue for 4.5 and the second was found to introduce a substantial
> performance regression on the syscall entry/exit path. I think Mark had
> an updated version to address that, so it would be easier not to have
> an old version sitting in some other queue!

I am not formally queueing them anywhere (like linux-next), though
now that you mention it, that's a pretty good idea - I'll talk to Steven
about that, assuming this merge window closes without the task
isolation stuff going in.

In the arch/tile code, we load the thread_info_flags and test them
against a bitmask before we call into C code, to avoid the various
overheads involved in the C path.  Perhaps that same strategy is all
that's needed for the arm64 code?  Hopefully you can get that
code merged up during the 4.5 window so I can use it as the new
baseline for the task isolation stuff.

Thanks!

--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com