On 8/10/20 3:26 PM, Jann Horn wrote: > On Mon, Aug 10, 2020 at 11:12 PM Jens Axboe <axboe@xxxxxxxxx> wrote: >> On 8/10/20 3:10 PM, Peter Zijlstra wrote: >>> On Mon, Aug 10, 2020 at 03:06:49PM -0600, Jens Axboe wrote: >>> >>>> should work as far as I can tell, but I don't even know if there's a >>>> reliable way to do task_in_kernel(). >>> >>> Only on NOHZ_FULL, and tracking that is one of the things that makes it >>> so horribly expensive. >> >> Probably no other way than to bite the bullet and just use TWA_SIGNAL >> unconditionally... > > Why are you trying to avoid using TWA_SIGNAL? Is there a specific part > of handling it that's particularly slow? Not particularly slow, but it's definitely heavier than TWA_RESUME. And as we're driving any pollable async IO through this, just trying to ensure it's as light as possible. It's not a functional thing, just efficiency. -- Jens Axboe
