@@ -775,8 +775,9 @@ static enum fullness_group fix_fullness_group(struct size_class *class,
static int get_pages_per_zspage(struct zs_pool *pool, int class_size)
{
int i, max_usedpc = 0;
- /* zspage order which gives maximum used size per KB */
- int max_usedpc_order = 1;
+ /* zspage size which gives maximum used size per KB */
+ int pages_per_zspage = 1;
+ int min_waste = INT_MAX;
for (i = 1; i <= pool->max_pages_per_zspage; i++) {
int zspage_size;
@@ -788,14 +789,19 @@ static int get_pages_per_zspage(struct zs_pool *pool, int class_size)
if (usedpc > max_usedpc) {
max_usedpc = usedpc;
- max_usedpc_order = i;
+ pages_per_zspage = i;
}
if (usedpc == 100)
break;
+
+ if (waste < min_waste) {
+ min_waste = waste;
+ pages_per_zspage = i;
+ }
}
- return max_usedpc_order;
+ return pages_per_zspage;
}
static struct zspage *get_zspage(struct page *page)
We currently decide the best zspage size by looking at used percentage value. This is not exactly enough as zspage usage percentage calculation is not accurate. For example, let's look at size class 208 pages per zspage wasted bytes used% 1 144 96 2 80 99 3 16 99 4 160 99 We will select 2 page per zspage configuration, as it is the first one to reach 99%. However, 3 pages per zspage wastes less memory. Hence we need to also consider wasted space metrics when device zspage size. Additionally, rename max_usedpc_order because it does not hold zspage order, it holds maximum pages per-zspage value. Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> --- mm/zsmalloc.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)