| From: | Marti Raudsepp <marti(at)juffo(dot)org> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | Thomas Pöhler <tp(at)turtle-entertainment(dot)de>, pgsql-performance(at)postgresql(dot)org, Felix Feinhals <ff(at)turtle-entertainment(dot)de>, Verteiler_A-Team <a-team(at)turtle-entertainment(dot)de>, Björn Metzdorf <bm(at)turtle-entertainment(dot)de> |
| Subject: | Re: high user cpu, massive SELECTs, no io waiting problem |
| Date: | 2011-02-16 13:44:06 |
| Message-ID: | AANLkTikwJ6WieNDmiS7n-6dBmGOvwjWW_Z8tOFPV=Ysr@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Feb 15, 2011 at 20:01, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
> run htop and look for red. if youi've got lots of red bar on each CPU
> but no io wait then it's waiting for memory access.
I don't think this is true. AFAICT the red bar refers to "system
time", time that's spent in the kernel -- either in syscalls or kernel
background threads.
Operating systems don't generally account memory accesses (cache
misses) for processes, if you don't specially ask for it. The closest
thing I know of is using Linux perf tools, e.g. "perf top -e
cache-misses". OProfile, DTrace and SystemTap can probably do
something similar.
Regards,
Marti
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