On 11/06/2017 08:30 PM, aravindan.muthuku...@intel.com wrote:
> From: Aravindan Muthukumar <aravindan.muthuku...@intel.com>
>
> Now the complexity has been reduced to O(1)
>
> Algorithm calculates the index using matrix method.
> Matrix arrangement is as below:
> Assuming PAGE_SIZE is 4096.
>
> 1*4096 2*4096 3*4096 4*4096
> 5*4096 6*4096 7*4096 8*4096
> 10*4096 12*4096 14*4096 16*4096
> 20*4096 24*4096 28*4096 32*4096
> ... ... ... ...
> ... ... ... ...
> ... ... ... max_cache_size
>
> From this matrix its clearly seen that every row
> follows the below way:
> ... ... ... n
> n+(1/4)n n+(1/2)n n+(3/4)n 2n
>
> Row is calculated as log2(size/PAGE_SIZE)
> Column is calculated as converting the difference
> between the elements to fit into power size of two
> and indexing it.
>
> Final Index is (row*4)+(col-1)
>
> Tested with Intel Mesa CI.
>
> Improves performance of 3DMark on BXT by 0.705966% +/- 0.229767% (n=20)
>
> v3: review comments implemented (Ian).
> v2: review comments implemented (Jason).
>
> Signed-off-by: Aravindan Muthukumar <aravindan.muthuku...@intel.com>
> Signed-off-by: Kedar Karanje <kedar.j.kara...@intel.com>
> Reviewed-by: Yogesh Marathe <yogesh.mara...@intel.com>
> ---
> src/mesa/drivers/dri/i965/brw_bufmgr.c | 38
> +++++++++++++++++++++++++++-------
> 1 file changed, 30 insertions(+), 8 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c
> b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> index 17036b5..9a423da 100644
> --- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
> +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> @@ -86,6 +86,8 @@
>
> #define memclear(s) memset(&s, 0, sizeof(s))
>
> +#define PAGE_SIZE 4096
> +
> #define FILE_DEBUG_FLAG DEBUG_BUFMGR
>
> static inline int
> @@ -180,19 +182,35 @@ bo_tile_pitch(struct brw_bufmgr *bufmgr, uint32_t
> pitch, uint32_t tiling)
> return ALIGN(pitch, tile_width);
> }
>
> +/*
> + * This function finds the correct bucket fit for the input size.
> + * The function works with O(1) complexity when the requested size
> + * was queried instead of iterating the size through all the buckets.
> + */
> static struct bo_cache_bucket *
> bucket_for_size(struct brw_bufmgr *bufmgr, uint64_t size)
> {
> - int i;
> + /* Calculating the pages and rounding up to the page size. */
> + const unsigned int pages = (size + PAGE_SIZE - 1) / PAGE_SIZE;
>
> - for (i = 0; i < bufmgr->num_buckets; i++) {
> - struct bo_cache_bucket *bucket = &bufmgr->cache_bucket[i];
> - if (bucket->size >= size) {
> - return bucket;
> - }
> - }
> + /* Finding the row number based on the calculated pages. */
> + const unsigned int rows = 30 - __builtin_clz((pages - 1) | 3);
>
> - return NULL;
Why did you make random (and incorrect) style changes and delete
(useful) comments from the code I sent?
> + const unsigned int row_max_pages = 4 << rows;
> + const unsigned int prev_row_max_pages = (row_max_pages / 2) & ~2;
> +
> + /* Finding the column number using column interval. */
> + int col_size_log2 = rows - 1;
> + col_size_log2 += (col_size_log2 < 0);
> +
> + const unsigned int col = ( (pages - prev_row_max_pages +
> + ( (1 << col_size_log2) - 1) ) >> col_size_log2 );
> +
> + /* Calculating the index based on the row and column. */
> + const unsigned int index = (rows * 4) + (col - 1);
> +
> + return (index < bufmgr->num_buckets) ?
> + &bufmgr->cache_bucket[index] : NULL;
> }
>
> int
> @@ -1254,6 +1272,10 @@ add_bucket(struct brw_bufmgr *bufmgr, int size)
> list_inithead(&bufmgr->cache_bucket[i].head);
> bufmgr->cache_bucket[i].size = size;
> bufmgr->num_buckets++;
> +
> + assert(bucket_for_size(bufmgr, size) == &bufmgr->cache_bucket[i]);
> + assert(bucket_for_size(bufmgr, size - 2048) == &bufmgr->cache_bucket[i]);
> + assert(bucket_for_size(bufmgr, size + 1) != &bufmgr->cache_bucket[i]);
> }
>
> static void
>
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