[mythtv-users] High mysql cpu usage

[Juhani Rautiainen]

On Mon, Jan 14, 2013 at 9:47 PM, Jarle Thorsen <jarlethorsen at gmail.com>wrote:

>
>
> I have now tried to have EIT completely off for the last 24H and it was
> like giving my mythbox a new life. No lagging at all. I have now turned on
> logging for slow mysql queries (longer than 20 seconds), and also turned on
> passive EIT scanning.
>
> And here we go again:
>
> 2013-01-14 20:36:10.697272 I [16203/16230] Scheduler scheduler.cpp:2129
> (HandleReschedule) - Reschedule requested for MATCH 0 0 0 - EITScanner
> 2013-01-14 20:36:57.013252 I [16203/16230] Scheduler scheduler.cpp:2242
> (HandleReschedule) - Scheduled 140 items in 46.2 = 45.42 match + 0.18 check
> + 0.60 place
>
> mysqld is again at 100% CPU in this time window, but the query is not
> logged by mysql as a slow query for some reason?
>

Probably lots of smaller queries. If those scheduler items are queried with
one query per item. Maximum time per query is something like
45.42/140=0.32s. But if this happens only with EIT scans it suggests that
this is concurrency issue. Which means that I was wrong with my idea with
changing execution plans.


> I'm guessing that the passive EIT scan gives it less data and that is the
> reason why it uses apx 40 seconds, compared to the 80+ seconds with active
> EIT scan enabled.
>

I'm just wondering why MySQL is busy looping on CPU. I have two DVB-C
tuners with passive EIT scan but I don't see this issue. I only have 25
channels and less recordings but it takes only fractions compared to above:

 mythlogserver: mythbackend[3434]: I Scheduler scheduler.cpp:2241
(HandleReschedule) Scheduled 30 items in 0.1 = 0.06 match + 0.01 check +
0.02 place



>
> --
> Jarle Thorsen
>

Juhani
-- 
Juhani Rautiainen                                   jrauti at iki.fi
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