On Mon, Jun 28, 2021 at 10:17:18AM -0400, Dan Schatzberg [off-list ref] wrote:

Agreed that exporting int_active_memcg is an implementation detail,
but would this prevent set_active_memcg from being inlined?

Non-inlining in the loop module doesn't seem like a big trouble. OTOH,
other callers may be more sensitive and would need to rely on inlining.
I can't currently think of a nice way to have both the exported and the
exlicitly inlined variant at once. It seems it's either API or perf
craft in the end but both are uncertain, so I guess the current approach
is fine in the end.

Yes it is intentional. All requests (not just aio) go through the loop
worker which grabs the blkcg reference in loop_queue_work() on
construction. So I believe grabbing a reference per request is
unnecessary.

Isn't there a window without the reference between loop_queue_rq and
loop_queue_work? I don't know, you seem to know better, so I'd suggest
dropping a comment line into the code explaining this.

Thanks,
Michal