On Wed, Jan 17, 2024 at 09:23:19AM +0000, Chengming Zhou wrote:
> Each swapfile has one rb-tree to search the mapping of swp_entry_t to
> zswap_entry, that use a spinlock to protect, which can cause heavy lock
> contention if multiple tasks zswap_store/load concurrently.
>
> Optimize the scalability problem by splitting the zswap rb-tree into
> multiple rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M),
> just like we did in the swap cache address_space splitting.
>
> Although this method can't solve the spinlock contention completely, it
> can mitigate much of that contention. Below is the results of kernel build
> in tmpfs with zswap shrinker enabled:
>
> linux-next zswap-lock-optimize
> real 1m9.181s 1m3.820s
> user 17m44.036s 17m40.100s
> sys 7m37.297s 4m54.622s
>
> So there are clearly improvements.
>
> Signed-off-by: Chengming Zhou <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
One minor nit:
> @@ -265,6 +266,10 @@ static bool zswap_has_pool;
> * helpers and fwd declarations
> **********************************/
>
> +#define swap_zswap_tree(entry) \
> + (&zswap_trees[swp_type(entry)][swp_offset(entry) \
> + >> SWAP_ADDRESS_SPACE_SHIFT])
Make this a static inline function instead?
On 2024/1/18 23:11, Johannes Weiner wrote:
> On Wed, Jan 17, 2024 at 09:23:19AM +0000, Chengming Zhou wrote:
>> Each swapfile has one rb-tree to search the mapping of swp_entry_t to
>> zswap_entry, that use a spinlock to protect, which can cause heavy lock
>> contention if multiple tasks zswap_store/load concurrently.
>>
>> Optimize the scalability problem by splitting the zswap rb-tree into
>> multiple rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M),
>> just like we did in the swap cache address_space splitting.
>>
>> Although this method can't solve the spinlock contention completely, it
>> can mitigate much of that contention. Below is the results of kernel build
>> in tmpfs with zswap shrinker enabled:
>>
>> linux-next zswap-lock-optimize
>> real 1m9.181s 1m3.820s
>> user 17m44.036s 17m40.100s
>> sys 7m37.297s 4m54.622s
>>
>> So there are clearly improvements.
>>
>> Signed-off-by: Chengming Zhou <[email protected]>
>
> Acked-by: Johannes Weiner <[email protected]>
>
> One minor nit:
>
>> @@ -265,6 +266,10 @@ static bool zswap_has_pool;
>> * helpers and fwd declarations
>> **********************************/
>>
>> +#define swap_zswap_tree(entry) \
>> + (&zswap_trees[swp_type(entry)][swp_offset(entry) \
>> + >> SWAP_ADDRESS_SPACE_SHIFT])
>
> Make this a static inline function instead?
Good suggestion, will do.
Thanks.