Re: [PATCH 5/6] mm/zswap: only support zswap_exclusive_loads_enabled

Chengming Zhou
2024-02-03T04:33:56Z

On 2024/2/3 00:26, Johannes Weiner wrote:
> On Fri, Feb 02, 2024 at 08:57:38PM +0800, Chengming Zhou wrote:
>> On 2024/2/2 02:12, Johannes Weiner wrote:
>>> Caching "swapout work" is helpful when the system is thrashing. Then
>>> recently swapped in pages might get swapped out again very soon. It
>>> certainly makes sense with conventional swap, because keeping a clean
>>> copy on the disk saves IO work and doesn't cost any additional memory.
>>>
>>> But with zswap, it's different. It saves some compression work on a
>>> thrashing page. But the act of keeping compressed memory contributes
>>> to a higher rate of thrashing. And that can cause IO in other places
>>> like zswap writeback and file memory.
>>
>> [...] A/B test kernel building in tmpfs directory, memory.max=2GB.
>> (zswap writeback enabled and shrinker_enabled, one 50GB swapfile)
>>
>> From the below results, exclusive mode has fewer scan and refault.
>>
>> zswap-invalidate-entry zswap-invalidate-entry-exclusive
>> real 63.80 63.01
>> user 1063.83 1061.32
>> sys 290.31 266.15
>> zswap-invalidate-entry zswap-invalidate-entry-exclusive
>> workingset_refault_anon 2383084.40 1976397.40
>> workingset_refault_file 44134.00 45689.40
>> workingset_activate_anon 837878.00 728441.20
>> workingset_activate_file 4710.00 4085.20
>> workingset_restore_anon 732622.60 639428.40
>> workingset_restore_file 1007.00 926.80
>> workingset_nodereclaim 0.00 0.00
>> pgscan 14343003.40 12409570.20
>> pgscan_kswapd 0.00 0.00
>> pgscan_direct 14343003.40 12409570.20
>> pgscan_khugepaged 0.00 0.00
>
> That's perfect. Thanks!
>
> Would you mind adding all of the above into the changelog?
Yeah, will do. Thanks!

>
> With that,
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>