[CRIU] [PATCH 0/8] vdso: Use gettimeofday() from vdso for timings

[Cyrill Gorcunov]

On Thu, Jul 25, 2019 at 11:01:06PM +0100, Dmitry Safonov wrote:
> Historically, PIE uses syscalls for printing timings.
> The idea was written a while ago here:
> https://github.com/checkpoint-restore/criu/issues/346
> 
> While at it, I've found that we print timings only in restorer blob, but
> not in parasite. It may be intentional or just missed
> std_log_set_start() call in parasite_init_daemon().
> Anyway, I've decided to keep it as-is for now.
> 
> Also, adding support for timings from vdso in ia32 turned to be more
> complex (see a comment in the last patch), so I decided to start from
> native applications.
> 
> I've measured the gain on zdtm tests:
> https://gist.github.com/0x7f454c46/7147b519e49f9ad01706c27ab1334fa7
> It seems that criu is really voluble on restoring mappings :)
> 
> Anyway, the gain is not as huge as I've expected (I thought we print
> much more), but still removes 50-100 syscalls per most of zdtm tests.
> And it doesn't bring much complexity as we already have all information
> about vdso mappings and symbol tables in restorer.
> So, remove syscalls for free and keep being the same informative.

Looks ok to me, thanks!

Reviewed-by: Cyrill Gorcunov <gorcunov at gmail.com>