在 2024/1/11 21:41, Johannes Weiner 写道:
On Thu, Jan 11, 2024 at 08:24:50PM +0800, Zhiguo Jiang wrote:
The parameter of target_memcg is NULL in workingset_eviction(), and
the lruvec obtained by mem_cgroup_lruvec(target_memcg, pgdat) is always
root_mem_cgroup->lruvec, rather than the lruvec of mem_cgroup where
folio is actually located.
WTF? No!
/*
* The memory cgroup that hit its limit and as a result is the
* primary target of this reclaim invocation.
*/
struct mem_cgroup *target_mem_cgroup;
The cgroup that is stored in the eviction cookie is the one whose
limit triggered the reclaim cycle. This is often several levels above
the cgroups that own the pages. Subsequent refaults need to be
evaluated at the eviction level:
/*
* The activation decision for this folio is made at the level
* where the eviction occurred, as that is where the LRU order
* during folio reclaim is being determined.
*
* However, the cgroup that will own the folio is the one that
* is actually experiencing the refault event.
*/
May I ask three questions: 1.I don't understand the meaning of this
paragraph. Can you explain it in detail ? 2.What are the characteristics
of folios managed by the root_mem_cgroup differring from other memcgs?
3.If shrink flow uses target_lruvec->anon_cost/file_cost, what is the
purposr of calculating the actual memcg's lruvec->anon_cost/file_cost in
lru_note_cost(), and the actual memcg's lruvec->anon_cost/file_cost
values are unused in shrink flow ? Thanks
Fix target_memcg to the memcg obtained by folio_memcg(folio).
Signed-off-by: Zhiguo Jiang <justinjiang@xxxxxxxx>
Nacked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Please take more time to read into the code you're proposing to
change. You made it sound like a trivial simplification, but this
totally screws up aging and pressure detection in containers.
