On Thu, Mar 31, 2016 at 10:09:56PM +0000, Holger Hoffstätte wrote: > > Hi, > > Jens mentioned on Twitter I should post my experience here as well, > so here we go. > > I've backported this series (incl. updates) to stable-4.4.x - not too > difficult, minus the NVM part which I don't need anyway - and have been > running it for the past few days without any problem whatsoever, with > GREAT success. > > My use case is primarily larger amounts of stuff (transcoded movies, > finished downloads, built Gentoo packages) that gets copied from tmpfs > to SSD (or disk) and every time that happens, the system noticeably > strangles readers (desktop, interactive shell). It does not really matter > how I tune writeback via the write_expire/dirty_bytes knobs or the > scheduler (and yes, I understand how they work); lowering the writeback > limits helped a bit but the system is still overwhelmed. Jacking up > deadline's writes_starved to unreasonable levels helps a bit, but in turn > makes all writes suffer. Anything else - even tried BFQ for a while, > which has its own unrelated problems - didn't really help either. Can you go back to your original kernel, and lower nr_requests to 8? Essentially all I see the block throttle doing is keeping the request queue depth to somewhere between 8-12 requests, rather than letting it blow out to near nr_requests (around 105-115), so it would be interesting to note whether the block throttling has any noticable difference in behaviour when compared to just having a very shallow request queue.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
