Re: [PATCH v3 3/4] mm/zswap: Add per-memcg stat for proactive writeback

[Hao Jia <jiahao.kernel@gmail.com>]

On 2026/5/30 04:01, Nhat Pham wrote:
> On Tue, May 26, 2026 at 4:46 AM Hao Jia <jiahao.kernel@gmail.com> wrote:
>>
>> From: Hao Jia <jiahao1@lixiang.com>
>>
>> Currently, zswap writeback can be triggered by either the pool limit
>> being hit or by the proactive writeback mechanism. However, the
>> existing 'zswpwb' metric in memory.stat and /proc/vmstat counts all
>> written back pages, making it difficult to distinguish between pages
>> written back due to the pool limit and those written back proactively.
>>
>> Add a new statistic 'zswpwb_proactive' to memory.stat and /proc/vmstat.
>> This counter tracks the number of pages written back due to proactive
>> writeback. This allows users to better monitor and tune the proactive
>> writeback mechanism.
>>
>> Signed-off-by: Hao Jia <jiahao1@lixiang.com>
>> ---
>>   Documentation/admin-guide/cgroup-v2.rst |  4 +++
>>   include/linux/vm_event_item.h           |  1 +
>>   mm/memcontrol.c                         |  1 +
>>   mm/vmstat.c                             |  1 +
>>   mm/zswap.c                              | 41 ++++++++++++++++++-------
>>   5 files changed, 37 insertions(+), 11 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
>> index 6564abf0dec5..7d65aef83f7b 100644
>> --- a/Documentation/admin-guide/cgroup-v2.rst
>> +++ b/Documentation/admin-guide/cgroup-v2.rst
>> @@ -1748,6 +1748,10 @@ The following nested keys are defined.
>>            zswpwb
>>                  Number of pages written from zswap to swap.
>>
>> +         zswpwb_proactive
>> +               Number of pages written from zswap to swap by proactive
>> +               writeback. This is a subset of zswpwb.
>> +
> 
> nit: I think this is specifically the zswap_writeback_only mode right?
> 
> Technically, normal proactive reclaim (memory.reclaim) can also hit zswap :)
> 
> Maybe some clarification here?

Thanks for the review. I will clarify this further in the next version.

Thanks,
Hao