On Sat, Sep 26, 2020 at 1:51 PM Julien Rouhaud <rjuju...@gmail.com> wrote:
> On Sat, Sep 26, 2020 at 8:17 AM Andy Fan <zhihui.fan1...@gmail.com> wrote: > > > > As for the testing with cache considered, I found how to estimate cache > hit > > ratio is hard or how to control a hit ratio to test is hard. Recently I > am thinking > > a method that we can get a page_reads, shared_buffer_hit from pg_kernel > > and the real io (without the file system cache hit) at os level (just as > what > > iotop/pidstat do). then we can know the shared_buffer hit ratio and file > system > > cache hit ratio (assume it will be stable after a long run). and then do > a testing. > > However this would be another branch of manual work and I still have not > got > > it done until now. > > FWIW pg_stat_kcache [1] extension accumulates per (database, user, > queryid) physical reads and writes, so you can easily compute a > shared_buffers / IO cache / disk hit ratio. > > [1] https://github.com/powa-team/pg_stat_kcache > WOW, this would be a good extension for this purpose. Thanks for sharing it. -- Best Regards Andy Fan
