On Thu, Sep 24, 2015 at 01:43:24AM +0200, Marc Lehmann wrote: > On Thu, Sep 24, 2015 at 01:30:22AM +0200, Marc Lehmann <schm...@schmorp.de> > wrote: > > > One thing I note is that gc_min_sleep_time is not be set in your script, > > > so in some condition gc may still do the sleep with gc_min_sleep_time (30 > > > seconds by default) instead of gc_max_sleep_time which we expect. > > > > Ah, sorry, I actually set gc_min_sleep_time to 100, but forgot to include > > it. > > Sorry, that sounded confusing - I set it to 100 in previous tests, and forgot > to include it, so it was running with 30000. When experimenting, I actually > do get the gc to do more frequent operations now. > > Is there any obvious harm setting it to a very low value (such as 100 or 10)? > > I assume all it does is have less time buffer between the last operation > and the gc starting. When I write in batches, or when I know the fs will be > idle, there shouldn't be any harm, performance wise, of letting it work all > the time.
Yeah, I don't think it does matter with very small time periods, since the timer is set after background GC is done. But, we use msecs_to_jiffies(), so hope not to use something like 10 ms, since each backgroudn GC conducts reading victim blocks into page cache and then just sets them as dirty. That indicates, after a while, we hope flusher will write them all to disk and finally we got a free section. So, IMO, we need to give some time slots to flusher as well. For example, if write bandwidth is 30MB/s and section size is 128MB, it needs about 4secs to write one section. So, how about setting - gc_min_time to 1~2 secs, - gc_max_time to 3~4 secs, - gc_idle_time to 10 secs, - reclaim_segments to 64 (sync when 1 section becomes prefree) Thanks, > > -- > The choice of a Deliantra, the free code+content MORPG > -----==- _GNU_ http://www.deliantra.net > ----==-- _ generation > ---==---(_)__ __ ____ __ Marc Lehmann > --==---/ / _ \/ // /\ \/ / schm...@schmorp.de > -=====/_/_//_/\_,_/ /_/\_\ ------------------------------------------------------------------------------ _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
