> On Sep 10, 2021, at 12:08 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Fri, Sep 10, 2021 at 07:00:08PM +0000, Song Liu wrote: > >> Hmm.. not really. We call migrate_disable() before entering the BPF program. >> And the helper calls snapshot_branch_stack() inside the BPF program. To move >> it to before migrate_disable(), we will have to add a "whether to snapshot >> branch stack" check before entering the BPF program. This check, while is >> cheap, is added to all BPF programs on this hook, even when the program does >> not use snapshot at all. So we would rather keep all logic inside the helper, >> and not touch the common path. > > Moo :/ Because I also really don't want to expose struct rq, it's > currently nicely squirelled away in kernel/sched/ and doesn't get > anywhere near include/. This matches my guess, so I didn't go too far on that direction. :-) > > A well, maybe we can do something clever with migrate_disable() itself. > I'll put it on this endless todo list ;-) Awesome! Thanks, Song
