On Tue 19-01-21 11:58:42, Johannes Weiner wrote:

On Tue, Jan 19, 2021 at 01:27:44PM +0800, Muchun Song wrote:

quoted

The current memcg will be freed soon, so updating it's vmstat and
vmevent values is pointless. Just skip updating it.

Signed-off-by: Muchun Song <redacted>

Oof, that's pretty subtle! Somebody trying to refactor that code for
other purposes may not immediately notice that optimization and add
potentially tedious bugs.

Absolutely agreed!

How much does this save? Cgroup creation and deletion isn't really
considered a hot path. It takes global locks and such...

This is not the first time when an (micro)optimization is posted without
any data showing benefit or otherwise appealing justification. Sigh.

-- 
Michal Hocko
SUSE Labs