On Mon, May 11, 2020 at 10:53:05PM +0200, Giuseppe Bilotta wrote: > Hello Piergiorgio, > > On Mon, May 11, 2020 at 6:15 PM Piergiorgio Sartor > <piergiorgio.sartor@xxxxxxxx> wrote: > > Hi again! > > > > I made a quick test. > > I disabled the lock / unlock in raid6check. > > > > With lock / unlock, I get around 1.2MB/sec > > per device component, with ~13% CPU load. > > Wihtout lock / unlock, I get around 15.5MB/sec > > per device component, with ~30% CPU load. > > > > So, it seems the lock / unlock mechanism is > > quite expensive. > > > > I'm not sure what's the best solution, since > > we still need to avoid race conditions. > > > > Any suggestion is welcome! > > Would it be possible/effective to lock multiple stripes at once? Lock, > say, 8 or 16 stripes, process them, unlock. I'm not familiar with the > internals, but if locking is O(1) on the number of stripes (at least > if they are consecutive), this would help reduce (potentially by a > factor of 8 or 16) the costs of the locks/unlocks at the expense of > longer locks and their influence on external I/O. Probabily possible, from the technical point of view, even if I do not know either the effect. >From the coding point of view, a bit tricky, boundary conditions and so on must be properly considered. > > -- > Giuseppe "Oblomov" Bilotta -- piergiorgio
