Re: [Patch] blkiomon: repost with some fixes and improvements

["Alan D. Brunelle" <Alan.Brunelle@hp.com>]

Török Edwin wrote:
> On 2008-07-18 13:31, Martin Peschke wrote:
>> recent changes:
>> - added man page
>> - beautified human-readable output
>> - fixed an x86 compile error caused by incomplete endianess handling
>> - fixed some x86 __u64 vs. unsigned long compiler warnings
>> - fixed checking of a command line argument
>>
>>
>> blkiomon periodicaly generates per devive request size and request latency
>> statistics from blktrace data. It provides histograms as well as data that
>>   
> 
> Does it also measure latency caused by the request queues being full?
> (which happens around here):
> blk-core.c:get_request:
> /*
>                      * The queue is full and the allocating
>                      * process is not a "batcher", and not
>                      * exempted by the IO scheduler
>                      */
>                     goto out;
> 
> That would be very useful to trace some high latencies I am seeing, see
> discussion here:
> http://lkml.org/lkml/2008/7/12/104
> 
> Best regards,
> --Edwin

Hi Edwin -

It would probably be pretty hard to do so - Martin is mostly interested
in issue & complete information. The stuff you needs comes from sleep
requests.

The btt tool is static, but does output some data concerning the amount
of time spent "sleeping" - waiting for a request to be made available.
(But only for the whole duration of the run, you're looking for an
instantaneous output.)

I've also looked at seekwatcher - but it too just looks at the issue &
complete stuff, but I will see if there is some way of handling sleep
request stuff "live".

Alan