Re: [monit] Quad Core Monitoring

[Martin Pala]

Monit can monitor "unlimited" number of CPUs ... each core is counted as 
one CPU (regardless in which socket it sits). CPU usage of multicore and 
singlecore machines whether single CPU or SMP can be monitored using 
existing monit capabilities.

Regarding mysql ... it can have several threads and each of these 
threads can be scheduled on different core/CPU and run in parallel. You 
never know on which core it runs unless you use resource management - 
for example Solaris allows you to bind the specific applications to 
specific resource pools which can define CPU boundary. Without the 
resource management, the process can be switched by the scheduler freely 
(including thread migrations).


Martin



address@hidden wrote:
> Thanks, but I don't think that would work.  If all four processors were 
> above 25%, it would give a false positive.  Am I correct in thinking 
> that monit doesn't actually have the capability to monitor more than one 
> cpu?  Maybe this should be a wishlist item?
>
>
> On Tue, Apr 29, 2008 at 12:34 PM, Martin Pala <address@hidden 
> <mailto:address@hidden>> wrote:
>
>     Monit is reporting the CPU usage as total (corresponding to first
>     example of top).
>
>     If the application will get 100% of one core on 4-core system, it's
>     CPU usage should be reported by monit is 25% (since 4 * 25% = 100%).
>
>     You can thus use rule like this:
>
>      if cpu usage > 25% then restart
>
>     Martin
>
>
>
>
>     address@hidden <mailto:address@hidden> wrote:
>
>         We have an issue were mysqld hogs up 100% of one of our cpu
>         cores from time to time.  How can I configure monit to restart
>         mysqld when this happens.
>         For an example of what I am talking about, top normally shows
>         only one cpu but if you press '1' it will show all the cpus.
>         (normal top)
>         top - 18:13:11 up 10 days, 21:59,  1 user,  load average: 1.56,
>         1.81, 2.08
>         Tasks: 186 total,   5 running, 181 sleeping,   0 stopped,   0 zombie
>         Cpu(s): 31.6% us,  7.6% sy,  0.0% ni, 60.8% id,  0.0% wa,  0.0%
>         hi,  0.0% si
>
>         (top after pressing '1')
>         top - 18:13:54 up 10 days, 22:00,  1 user,  load average: 1.73,
>         1.81, 2.07
>         Tasks: 185 total,   3 running, 182 sleeping,   0 stopped,   0 zombie
>         Cpu0  : 29.4% us,  5.9% sy,  0.0% ni, 63.9% id,  0.7% wa,  0.0%
>         hi,  0.0% si
>         Cpu1  : 27.9% us,  5.6% sy,  0.0% ni, 65.5% id,  1.0% wa,  0.0%
>         hi,  0.0% si
>         Cpu2  : 23.1% us,  5.7% sy,  0.0% ni, 70.6% id,  0.7% wa,  0.0%
>         hi,  0.0% si
>         Cpu3  : 25.3% us,  6.2% sy,  0.0% ni, 67.5% id,  1.0% wa,  0.0%
>         hi,  0.0% si
>
>         (sample when mysqld is hogging cpu time)
>         top - 18:13:54 up 10 days, 22:00,  1 user,  load average: 1.73,
>         1.81, 2.07
>         Tasks: 185 total,   3 running, 182 sleeping,   0 stopped,   0 zombie
>         Cpu0  : 100 % us,  5.9% sy,  0.0% ni, 63.9% id,  0.7% wa,  0.0%
>         hi,  0.0% si
>         Cpu1  : 7.9% us,  5.6% sy,  0.0% ni, 65.5% id,  1.0% wa,  0.0%
>         hi,  0.0% si
>         Cpu2  : 3.1% us,  5.7% sy,  0.0% ni, 70.6% id,  0.7% wa,  0.0%
>         hi,  0.0% si
>         Cpu3  : 5.3% us,  6.2% sy,  0.0% ni, 67.5% id,  1.0% wa,  0.0%
>         hi,  0.0% si
>
>         So, how do I get monit to restart mysqld when just one cpu is
>         pegged at 100%?  It's not always Cpu0, it could be any of them.
>
>         Thanks,
>
>
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