[Mesa-dev] [PATCH 4/4] util/disk_cache: use a thread queue to write to shader cache

[Grazvydas Ignotas]

On Mon, Mar 13, 2017 at 3:01 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> This should help reduce any overhead added by the shader cache
> when programs are not found in the cache.
>
> To avoid creating any special function just for the sake of the
> tests we add a one second delay whenever we call dick_cache_put()
> to give it time to finish.
> ---
>  src/compiler/glsl/tests/cache_test.c | 49 +++++++++++++++++++++++++++++++-----
>  src/util/disk_cache.c                | 41 ++++++++++++++++++++----------
>  2 files changed, 71 insertions(+), 19 deletions(-)
>
> diff --git a/src/compiler/glsl/tests/cache_test.c b/src/compiler/glsl/tests/cache_test.c
> index 6451e65..f8259e0 100644
> --- a/src/compiler/glsl/tests/cache_test.c
> +++ b/src/compiler/glsl/tests/cache_test.c
> @@ -25,20 +25,21 @@
>
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <stdbool.h>
>  #include <string.h>
>  #include <ftw.h>
>  #include <errno.h>
>  #include <stdarg.h>
>  #include <inttypes.h>
>  #include <limits.h>
> +#include <time.h>
>  #include <unistd.h>
>
>  #include "util/mesa-sha1.h"
>  #include "util/disk_cache.h"
>
>  bool error = false;
>
>  #ifdef ENABLE_SHADER_CACHE
>
>  static void
> @@ -224,20 +225,27 @@ does_cache_contain(struct disk_cache *cache, cache_key key)
>
>     if (result) {
>        free(result);
>        return true;
>     }
>
>     return false;
>  }
>
>  static void
> +wait_one_second()
> +{
> +    unsigned wait_time = time(0) + 1;
> +    while (time(0) < wait_time);
> +}

If you enter this function at an unfortunate time (just as the second
is about to change) the function will not wait at all, so this will
cause spurious test failures. If you just sleep() it will waste
everyone's time on make check.

It looks like flushing the queue in disk_cache_get() should solve
this, it might be needed anyway because the app may request something
while the thread is still writing it out?

Gražvydas