On Fri, Oct 02 2009, Ingo Molnar wrote: > > * Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: > > > It's not hard to make the latency good, the hard bit is making sure we > > also perform well for all other scenarios. > > Looking at the numbers from Mike: > > | dd competing against perf stat -- konsole -e exec timings, 5 back to > | back runs > | Avg > | before 9.15 14.51 9.39 15.06 9.90 11.6 > | after [+patch] 1.76 1.54 1.93 1.88 1.56 1.7 > > _PLEASE_ make read latencies this good - the numbers are _vastly_ > better. We'll worry about the 'other' things _after_ we've reached good > latencies. > > I thought this principle was a well established basic rule of Linux IO > scheduling. Why do we have to have a 'latency vs. bandwidth' discussion > again and again? I thought latency won hands down. It's really not that simple, if we go and do easy latency bits, then throughput drops 30% or more. You can't say it's black and white latency vs throughput issue, that's just not how the real world works. The server folks would be most unpleased. -- Jens Axboe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
