Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2009-04-04 Thread Greg Smith
On Sat, 4 Apr 2009, Josh Berkus wrote: Have you sent this to any Linux kernel engineers? My experience is that they're fairly responsive to this sort of thing. I'm going to submit an updated report to LKML once I get back from East, I want to test against the latest kernel first. -- * Greg

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2009-04-04 Thread Josh Berkus
On 4/4/09 9:07 AM, Greg Smith wrote: On Tue, 31 Mar 2009, Kevin Grittner wrote: On Thu, Apr 17, 2008 at 7:26 PM, Greg Smith wrote: On this benchmark 2.6.25 is the worst kernel yet: I don't remember seeing a follow-up on this issue from last year. Are there still any particular kernels to a

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2009-04-04 Thread Greg Smith
On Tue, 31 Mar 2009, Kevin Grittner wrote: On Thu, Apr 17, 2008 at 7:26 PM, Greg Smith wrote: On this benchmark 2.6.25 is the worst kernel yet: I don't remember seeing a follow-up on this issue from last year. Are there still any particular kernels to avoid based on this? I just discover

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2009-03-31 Thread Greg Smith
On Tue, 31 Mar 2009, Kevin Grittner wrote: On Thu, Apr 17, 2008 at 7:26 PM, Greg Smith wrote: On this benchmark 2.6.25 is the worst kernel yet: It seems I have a lot of work ahead of me here to nail down and report what's going on here. I don't remember seeing a follow-up on this issue

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2009-03-31 Thread Kevin Grittner
>>> On Thu, Apr 17, 2008 at 7:26 PM, Greg Smith wrote: > On this benchmark 2.6.25 is the worst kernel yet: > It seems I have a lot of work ahead of me here > to nail down and report what's going on here. I don't remember seeing a follow-up on this issue from last year. Are there still any p

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-05-18 Thread Greg Smith
On Fri, 18 Apr 2008, Matthew wrote: So what happens if you run pgbench on a separate machine to the server? Does the problem still exist in that case? It does not. At the low client counts, there's a big drop-off relative to running on localhost just because of running over the network. But

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-18 Thread Greg Smith
On Fri, 18 Apr 2008, Matthew wrote: You may also be seeing processes forced to switch between CPUs, which breaks the caches even more. So what happens if you run pgbench on a separate machine to the server? Does the problem still exist in that case? I haven't run that test yet but will befor

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-18 Thread Matthew
On Thu, 17 Apr 2008, I wrote: There is only one central tunable (you have to switch on CONFIG_SCHED_DEBUG): /proc/sys/kernel/sched_granularity_ns which can be used to tune the scheduler from 'desktop' (low latencies) to 'server' (go

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Greg Smith
On Fri, 18 Apr 2008, Tom Lane wrote: Yeah, it's starting to be obvious that we'd better not ignore sysbench as "not our problem". Do you have any roadmap on what needs to be done to it? Just dug into this code again for a minute and it goes something like this: 1) Wrap the write statement

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Tom Lane
Greg Smith <[EMAIL PROTECTED]> writes: > This is what happens when the kernel developers are using results from a > MySQL tool to optimize things I guess. It seems I have a lot of work > ahead of me here to nail down and report what's going on here. Yeah, it's starting to be obvious that we'd b

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Greg Smith
On Thu, 17 Apr 2008, [EMAIL PROTECTED] wrote: report this to the kernel list so that they know, and be ready to test fixes. Don't worry, I'm on that. I'm already having enough problems with database performance under Linux, if they start killing results on the easy benchmarks I'll really be

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread david
On Thu, 17 Apr 2008, Greg Smith wrote: On Thu, 17 Apr 2008, Matthew wrote: The last message in the thread says that 2.6.25-rc6 has the problem nailed. That was a month ago. So I guess, upgrade to 2.6.25, which was released today. Ah, even more support for me to distrust everything I read.

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Greg Smith
On Thu, 17 Apr 2008, Matthew wrote: The last message in the thread says that 2.6.25-rc6 has the problem nailed. That was a month ago. So I guess, upgrade to 2.6.25, which was released today. Ah, even more support for me to distrust everything I read. The change has flattened out things, so

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Greg Smith
On Thu, 17 Apr 2008, Jeffrey Baker wrote: This has been discussed recently on linux-kernel. Excellent pointer, here's direct to the interesting link there: http://marc.info/?l=linux-kernel&m=120574906013029&w=2 Ingo's test system has 16 cores and dives hard at >32 clients; my 4-core system

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Matthew
On Thu, 17 Apr 2008, Jeffrey Baker wrote: On Thu, Apr 17, 2008 at 12:58 AM, Greg Smith <[EMAIL PROTECTED]> wrote: So in the case of this simple benchmark, I see an enormous performance regression from the newest Linux kernel compared to a much older one. This has been discussed recently on li

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Jeffrey Baker
On Thu, Apr 17, 2008 at 12:58 AM, Greg Smith <[EMAIL PROTECTED]> wrote: > So in the case of this simple benchmark, I see an enormous performance > regression from the newest Linux kernel compared to a much older one. This has been discussed recently on linux-kernel. It's definitely a regression.

Re: [PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Matthew
On Thu, 17 Apr 2008, Greg Smith wrote: So in the case of this simple benchmark, I see an enormous performance regression from the newest Linux kernel compared to a much older one. I need to do some version bisection to nail it down for sure, but my guess is it's the change to the Completely Fa

[PERFORM] Strange behavior: pgbench and new Linux kernels

2008-04-17 Thread Greg Smith
This week I've finished building and installing OSes on some new hardware at home. I have a pretty standard validation routine I go through to make sure PostgreSQL performance is good on any new system I work with. Found a really strange behavior this time around that seems related to changes