[Mesa-dev] [PATCH 1/4] i965: Convert brw_bufmgr to use C11 mutexes instead of pthreads.

[Jason Ekstrand]

On September 24, 2017 01:02:21 Kenneth Graunke <kenneth at whitecape.org> wrote:
> There's no real advantage or disadvantage here, it's just for stylistic
> consistency with the rest of the codebase.

Didn't Kristian do a bunch of work done time ago to make mutexes faster by 
not using pthread on Linux?  If so, this should be an unnoticeable 
performance improvement.

--Jason

> ---
>  src/mesa/drivers/dri/i965/brw_bufmgr.c | 35 +++++++++++++++++-----------------
>  1 file changed, 17 insertions(+), 18 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c 
> b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> index 44aaf02ca9f..73a539db755 100644
> --- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
> +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> @@ -43,7 +43,6 @@
>  #include <string.h>
>  #include <unistd.h>
>  #include <assert.h>
> -#include <pthread.h>
>  #include <sys/ioctl.h>
>  #include <sys/stat.h>
>  #include <sys/types.h>
> @@ -107,7 +106,7 @@ struct bo_cache_bucket {
>  struct brw_bufmgr {
>     int fd;
>
> -   pthread_mutex_t lock;
> +   mtx_t lock;
>
>     /** Array of lists of cached gem objects of power-of-two sizes */
>     struct bo_cache_bucket cache_bucket[14 * 4];
> @@ -284,7 +283,7 @@ bo_alloc_internal(struct brw_bufmgr *bufmgr,
>        bo_size = bucket->size;
>     }
>
> -   pthread_mutex_lock(&bufmgr->lock);
> +   mtx_lock(&bufmgr->lock);
>     /* Get a buffer out of the cache if available */
>  retry:
>     alloc_from_cache = false;
> @@ -394,7 +393,7 @@ retry:
>     bo->cache_coherent = bufmgr->has_llc;
>     bo->index = -1;
>
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>
>     DBG("bo_create: buf %d (%s) %llub\n", bo->gem_handle, bo->name,
>         (unsigned long long) size);
> @@ -404,7 +403,7 @@ retry:
>  err_free:
>     bo_free(bo);
>  err:
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>     return NULL;
>  }
>
> @@ -485,7 +484,7 @@ brw_bo_gem_create_from_name(struct brw_bufmgr *bufmgr,
>      * alternating names for the front/back buffer a linear search
>      * provides a sufficiently fast match.
>      */
> -   pthread_mutex_lock(&bufmgr->lock);
> +   mtx_lock(&bufmgr->lock);
>     bo = hash_find_bo(bufmgr->name_table, handle);
>     if (bo) {
>        brw_bo_reference(bo);
> @@ -541,12 +540,12 @@ brw_bo_gem_create_from_name(struct brw_bufmgr *bufmgr,
>     DBG("bo_create_from_handle: %d (%s)\n", handle, bo->name);
>
>  out:
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>     return bo;
>
>  err_unref:
>     bo_free(bo);
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>     return NULL;
>  }
>
> @@ -651,14 +650,14 @@ brw_bo_unreference(struct brw_bo *bo)
>
>        clock_gettime(CLOCK_MONOTONIC, &time);
>
> -      pthread_mutex_lock(&bufmgr->lock);
> +      mtx_lock(&bufmgr->lock);
>
>        if (p_atomic_dec_zero(&bo->refcount)) {
>           bo_unreference_final(bo, time.tv_sec);
>           cleanup_bo_cache(bufmgr, time.tv_sec);
>        }
>
> -      pthread_mutex_unlock(&bufmgr->lock);
> +      mtx_unlock(&bufmgr->lock);
>     }
>  }
>
> @@ -1042,7 +1041,7 @@ brw_bo_wait(struct brw_bo *bo, int64_t timeout_ns)
>  void
>  brw_bufmgr_destroy(struct brw_bufmgr *bufmgr)
>  {
> -   pthread_mutex_destroy(&bufmgr->lock);
> +   mtx_destroy(&bufmgr->lock);
>
>     /* Free any cached buffer objects we were going to reuse */
>     for (int i = 0; i < bufmgr->num_buckets; i++) {
> @@ -1111,12 +1110,12 @@ brw_bo_gem_create_from_prime(struct brw_bufmgr 
> *bufmgr, int prime_fd)
>     struct brw_bo *bo;
>     struct drm_i915_gem_get_tiling get_tiling;
>
> -   pthread_mutex_lock(&bufmgr->lock);
> +   mtx_lock(&bufmgr->lock);
>     ret = drmPrimeFDToHandle(bufmgr->fd, prime_fd, &handle);
>     if (ret) {
>        DBG("create_from_prime: failed to obtain handle from fd: %s\n",
>            strerror(errno));
> -      pthread_mutex_unlock(&bufmgr->lock);
> +      mtx_unlock(&bufmgr->lock);
>        return NULL;
>     }
>
> @@ -1165,12 +1164,12 @@ brw_bo_gem_create_from_prime(struct brw_bufmgr 
> *bufmgr, int prime_fd)
>     /* XXX stride is unknown */
>
>  out:
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>     return bo;
>
>  err:
>     bo_free(bo);
> -   pthread_mutex_unlock(&bufmgr->lock);
> +   mtx_unlock(&bufmgr->lock);
>     return NULL;
>  }
>
> @@ -1202,7 +1201,7 @@ brw_bo_flink(struct brw_bo *bo, uint32_t *name)
>        if (drmIoctl(bufmgr->fd, DRM_IOCTL_GEM_FLINK, &flink))
>           return -errno;
>
> -      pthread_mutex_lock(&bufmgr->lock);
> +      mtx_lock(&bufmgr->lock);
>        if (!bo->global_name) {
>           bo->global_name = flink.name;
>           bo->reusable = false;
> @@ -1210,7 +1209,7 @@ brw_bo_flink(struct brw_bo *bo, uint32_t *name)
>
>           _mesa_hash_table_insert(bufmgr->name_table, &bo->global_name, bo);
>        }
> -      pthread_mutex_unlock(&bufmgr->lock);
> +      mtx_unlock(&bufmgr->lock);
>     }
>
>     *name = bo->global_name;
> @@ -1353,7 +1352,7 @@ brw_bufmgr_init(struct gen_device_info *devinfo, int fd)
>      */
>     bufmgr->fd = fd;
>
> -   if (pthread_mutex_init(&bufmgr->lock, NULL) != 0) {
> +   if (mtx_init(&bufmgr->lock, mtx_plain) != 0) {
>        free(bufmgr);
>        return NULL;
>     }
> --
> 2.14.1
>
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