On 4/15/21 12:40 PM, Johannes Weiner wrote:
On Tue, Apr 13, 2021 at 09:20:23PM -0400, Waiman Long wrote:
The caller of mod_memcg_lruvec_state() has both memcg and lruvec readily
available. So both of them are now passed to mod_memcg_lruvec_state()
and __mod_memcg_lruvec_state(). The __mod_memcg_lruvec_state() is
updated to allow either of the two parameters to be set to null. This
makes mod_memcg_lruvec_state() equivalent to mod_memcg_state() if lruvec
is null.
The new __mod_memcg_lruvec_state() function will be used in the next
patch as a replacement of mod_memcg_state() in mm/percpu.c for the
consolidation of the memory uncharge and vmstat update functions in
the kmem_cache_free() path.
This requires users who want both to pass a pgdat that can be derived
from the lruvec. This is error prone, and we just acked a patch that
removes this very thing from mem_cgroup_page_lruvec().
With the suggestion for patch 2, this shouldn't be necessary anymore,
though. And sort of underlines my point around that combined function
creating akwward code above and below it.
The reason of passing in the pgdat is because of the caching of vmstat
data. lruvec may be gone if the corresponding memory cgroup is removed,
but pgdat should stay put. That is why I put pgdat in the obj_stock for
caching. I could also put the node id instead of pgdat.
Cheers,
Longman
