On Thu, Nov 19, 2020 at 9:31 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Thu, Nov 19, 2020 at 09:19:35AM -0500, Willem de Bruijn wrote: > > But for epoll, this is inefficient: in ep_set_mstimeout it calls > > ktime_get_ts64 to convert timeout to an offset from current time, only > > to pass it to select_estimate_accuracy to then perform another > > ktime_get_ts64 and subtract this to get back to (approx.) the original > > timeout. > > > > How about a separate patch that adds epoll_estimate_accuracy with > > the same rules (wrt rt_task, current->timer_slack, nice and upper bound) > > but taking an s64 timeout. > > > > One variation, since it is approximate, I suppose we could even replace > > division by a right shift? > > > > After that, using s64 everywhere is indeed much simpler. And with that > > I will revise the new epoll_pwait2 interface to take a long long > > instead of struct timespec. > > I think the userspace interface should take a struct timespec > for consistency with ppoll and pselect. And epoll should use > poll_select_set_timeout() to convert the relative timeout to an absolute > endtime. Make epoll more consistent with select/poll, not less ... Okay. The absolute time is also needed for schedule_hrtimeout_range, so it could not be entirely avoided, anyway.
