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

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

On 2026/5/14 05:21, Nhat Pham wrote:
> On Mon, May 11, 2026 at 3:52 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                              | 11 +++++++++--
>>   5 files changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
>> index 05b664b3b3e8..29a189b18efc 100644
>> --- a/Documentation/admin-guide/cgroup-v2.rst
>> +++ b/Documentation/admin-guide/cgroup-v2.rst
>> @@ -1734,6 +1734,10 @@ 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.
>> +
>>            zswap_incomp
>>                  Number of incompressible pages currently stored in zswap
>>                  without compression. These pages could not be compressed to
> 
> nit: once we have reached consensus on an interface, can you add
> documentation for the new knob in cgroup v2 doc and zswap doc too, and
> how it interacts with the other interface (memory.zswap.writeback,
> shrinker_enabled sysfs knob).
> 
> A kselftest would be very much appreciated too :)

Thanks, will do in v2

Thanks,
Hao