Re: devstat overhead VS precision

2013-04-15 Thread Poul-Henning Kamp
In message <516c71bc.4000...@freebsd.org>, Alexander Motin writes: >On 15.04.2013 23:43, Poul-Henning Kamp wrote: >> In message <516c515a.9090...@freebsd.org>, Alexander Motin writes: >> >> For tuning anything on a non-ridiculous SSD device or modern >> harddisks, it will be useless because of the

Re: devstat overhead VS precision

2013-04-15 Thread Alexander Motin
On 15.04.2013 23:43, Poul-Henning Kamp wrote: In message <516c515a.9090...@freebsd.org>, Alexander Motin writes: I propose to switch that statistics from using binuptime() to getbinuptime() to solve the problem globally. No objections here, but I wonder if you were able to compare the result

Re: devstat overhead VS precision

2013-04-15 Thread Poul-Henning Kamp
In message <516c515a.9090...@freebsd.org>, Alexander Motin writes: >>> I propose to switch that >>> statistics from using binuptime() to getbinuptime() to solve the problem >>> globally. >> No objections here, but I wonder if you were able to compare the results >> somehow before and after the ch

Re: devstat overhead VS precision

2013-04-15 Thread Konstantin Belousov
On Mon, Apr 15, 2013 at 09:37:30PM +0200, Pawel Jakub Dawidek wrote: > On Mon, Apr 15, 2013 at 10:18:15PM +0300, Konstantin Belousov wrote: > > On Mon, Apr 15, 2013 at 08:42:03PM +0200, Pawel Jakub Dawidek wrote: > > > On a mostly unrelated note when two threads (T0 and T1) call get*time() > > > on

Re: devstat overhead VS precision

2013-04-15 Thread Pawel Jakub Dawidek
On Mon, Apr 15, 2013 at 10:18:15PM +0300, Konstantin Belousov wrote: > On Mon, Apr 15, 2013 at 08:42:03PM +0200, Pawel Jakub Dawidek wrote: > > On a mostly unrelated note when two threads (T0 and T1) call get*time() > > on two different cores, but T0 does that a bit earlier is it possible > > that

Re: devstat overhead VS precision

2013-04-15 Thread Konstantin Belousov
On Mon, Apr 15, 2013 at 08:42:03PM +0200, Pawel Jakub Dawidek wrote: > On a mostly unrelated note when two threads (T0 and T1) call get*time() > on two different cores, but T0 does that a bit earlier is it possible > that T0 can get later time than T1? Define earlier first. If you have taken suff

Re: devstat overhead VS precision

2013-04-15 Thread Alexander Motin
On 15.04.2013 21:42, Pawel Jakub Dawidek wrote: On Sat, Apr 13, 2013 at 12:59:49PM +0300, Alexander Motin wrote: Hi. It is long known that collecting disk and GEOM statistics may cause significant processing overhead under high IOPS. On my recent high-IOPS benchmarks performance difference was

Re: devstat overhead VS precision

2013-04-15 Thread Pawel Jakub Dawidek
On Sat, Apr 13, 2013 at 12:59:49PM +0300, Alexander Motin wrote: > Hi. > > It is long known that collecting disk and GEOM statistics may cause > significant processing overhead under high IOPS. On my recent high-IOPS > benchmarks performance difference was reaching three times! Last time > situ

devstat overhead VS precision

2013-04-13 Thread Alexander Motin
Hi. It is long known that collecting disk and GEOM statistics may cause significant processing overhead under high IOPS. On my recent high-IOPS benchmarks performance difference was reaching three times! Last time situation improved a lot by more active use of TSC, but there are still many sy