Re: [PATCH v2 4/6] util/oslib-posix: Avoid creating a single thread with MADV_POPULATE_WRITE

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* David Hildenbrand (david@redhat.com) wrote:
> Let's simplify the case when we only want a single thread and don't have
> to mess with signal handlers.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  util/oslib-posix.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index a1d309d495..1483e985c6 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -568,6 +568,14 @@ static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages,
>      }
>  
>      if (use_madv_populate_write) {
> +        /* Avoid creating a single thread for MADV_POPULATE_WRITE */
> +        if (context.num_threads == 1) {
> +            if (qemu_madvise(area, hpagesize * numpages,
> +                             QEMU_MADV_POPULATE_WRITE)) {

Do you never have to fall back if this particular memory region is the
one that can't do madv?

Dave

> +                return true;
> +            }
> +            return false;
> +        }
>          touch_fn = do_madv_populate_write_pages;
>      } else {
>          touch_fn = do_touch_pages;
> -- 
> 2.31.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK