Hello,
On Sat, Jan 11, 2014 at 03:43:07PM +0800, Cai Liu wrote:
> zswap can support multiple swapfiles. So we need to check
> all zbud pool pages in zswap.
True but this patch is rather costly that we should iterate
zswap_tree[MAX_SWAPFILES] to check it. SIGH.
How about defining zswap_tress as linked list instead of static
array? Then, we could reduce unnecessary iteration too much.
Other question:
Why do we need to update zswap_pool_pages too frequently?
As I read the code, I think it's okay to update it only when user
want to see it by debugfs and zswap_is_full is called.
So could we optimize it out?
>
> Signed-off-by: Cai Liu <cai.liu@xxxxxxxxxxx>
> ---
> mm/zswap.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index d93afa6..2438344 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -291,7 +291,6 @@ static void zswap_free_entry(struct zswap_tree *tree,
> zbud_free(tree->pool, entry->handle);
> zswap_entry_cache_free(entry);
> atomic_dec(&zswap_stored_pages);
> - zswap_pool_pages = zbud_get_pool_size(tree->pool);
> }
>
> /* caller must hold the tree lock */
> @@ -405,10 +404,24 @@ cleanup:
> /*********************************
> * helpers
> **********************************/
> +static u64 get_zswap_pool_pages(void)
> +{
> + int i;
> + u64 pool_pages = 0;
> +
> + for (i = 0; i < MAX_SWAPFILES; i++) {
> + if (zswap_trees[i])
> + pool_pages += zbud_get_pool_size(zswap_trees[i]->pool);
> + }
> + zswap_pool_pages = pool_pages;
> +
> + return pool_pages;
> +}
> +
> static bool zswap_is_full(void)
> {
> return (totalram_pages * zswap_max_pool_percent / 100 <
> - zswap_pool_pages);
> + get_zswap_pool_pages());
> }
>
> /*********************************
> @@ -716,7 +729,6 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>
> /* update stats */
> atomic_inc(&zswap_stored_pages);
> - zswap_pool_pages = zbud_get_pool_size(tree->pool);
>
> return 0;
>
> --
> 1.7.10.4
>
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--
Kind regards,
Minchan Kim
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