On Wed, Sep 12, 2018 at 12:27:46PM -0700, Liu Bo wrote: > On Wed, Sep 12, 2018 at 09:37:20AM +0300, Nikolay Borisov wrote: > > > > > > On 12.09.2018 01:06, Liu Bo wrote: > > > As long as @eb is marked with EXTENT_BUFFER_DIRTY, all of its pages > > > are dirty, so no need to set pages dirty again. > > > > > > Signed-off-by: Liu Bo <bo....@linux.alibaba.com> > > > > Does make it any performance difference, numbers? > > > > To be honest, the performance difference would be trivial in a normal > big test round. But I just looked into the difference from my ftrace, > removing the loop can reduce the time spent by 10us in my box.
10us was for the case where the pages were dirty already and the for cycle was then skipped? set_page_dirty is not lightweight, calls down to various functions and holds locks. I can't tell if this is still fast enough on your machine so that it really takes 10us. The conditional dirtying is definetelly worth though, Reviewed-by: David Sterba <dste...@suse.com>
