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SubjectRe: [Patch 3.11.7 1/1]mm: remove and free expired data in time in zswap
On 11/08/2013 05:50 PM, changkun.li wrote:
> In zswap, store page A to zbud if the compression ratio is high, insert
> its entry into rbtree. if there is a entry B which has the same offset
> in the rbtree.Remove and free B before insert the entry of A.
>
> case:
> if the compression ratio of page A is not high, return without checking
> the same offset one in rbtree.
>
> if there is a entry B which has the same offset in the rbtree. Now, we
> make sure B is invalid or expired. But the entry and compressed memory
> of B are not freed in time.
>
> Because zswap spaces data in memory, it makes the utilization of memory
> lower. the other valid data in zbud is writeback to swap device more
> possibility, when zswap is full.
>
> So if we make sure a entry is expired, free it in time.
>
> Signed-off-by: changkun.li<xfishcoder@gmail.com>
> ---
> mm/zswap.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index cbd9578..90a2813 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -596,6 +596,7 @@ fail:
> return ret;
> }
>
> +static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t
> offset);
> /*********************************
> * frontswap hooks
> **********************************/
> @@ -614,7 +615,7 @@ static int zswap_frontswap_store(unsigned type,
> pgoff_t offset,
>
> if (!tree) {
> ret = -ENODEV;
> - goto reject;
> + goto nodev;
> }
>
> /* reclaim space if needed */
> @@ -695,6 +696,8 @@ freepage:
> put_cpu_var(zswap_dstmem);
> zswap_entry_cache_free(entry);
> reject:
> + zswap_frontswap_invalidate_page(type, offset);

I'm afraid when arrives here zswap_rb_search(offset) will always return
NULL entry. So most of the time, it's just waste time to call
zswap_frontswap_invalidate_page() to search rbtree.

--
Regards,
-Bob


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