On Tue, Dec 15, 2020 at 08:59:11AM +0100, Peter Zijlstra wrote: > On Tue, Dec 15, 2020 at 11:36:35AM +0800, Li, Aubrey wrote: > > On 2020/12/15 0:48, Peter Zijlstra wrote: > > > We compute the average cost of the total scan, but then use it as a > > > per-cpu scan cost when computing the scan proportion. Fix this by > > > properly computing a per-cpu scan cost. > > > > > > This also fixes a bug where we would terminate early (!--nr, case) and > > > not account that cost at all. > > > > I'm a bit worried this may introduce a regression under heavy load. > > The overhead of adding another cpu_clock() and calculation becomes > > significant when sis_scan is throttled by nr. > > The thing is, the code as it exists today makes no sense what so ever.
Which makes it very hard to reason about or change in a "safe" manner as all sorts of counter-intuitive effects occur. The series is queued and running and takes 1-2 days. I haven't reviewed the patches properly (holiday) but it'll be interesting to get some provisional data at least. -- Mel Gorman SUSE Labs
