On Wed, Jan 09, 2019 at 01:37:23PM -0500, Waiman Long wrote: > On 01/09/2019 01:24 PM, Matthew Wilcox wrote: > > Did you even try just using the general purpose infrastructure that's > > in place? If that shows a performance problem _then_ it's time to make > > this special snowflake just a little more special. Not before. > > I have looked into the percpu counter code. There are two aspects that I > don't like to introduce to the interrupt handler's code path for > updating the counts. > > 1) There is a raw spinlock in the percpu_counter structure that may need > to be acquired in the update path. This can be a performance drag > especially if lockdep is enabled. > > 2) The percpu_counter structure is 40 bytes in size on 64-bit systems > compared with just 8 bytes for the percpu count pointer and an > additional 4 bytes that I introduced in patch 2. With thousands of irq > descriptors, it can consume quite a lot more memory. Memory consumption > was a point that you brought up in one of your previous mails. Then _argue that_. Don't just go off and do something random without explaining to the rest of us why we're wrong.
