Messages in this thread | | | Date | Mon, 23 Oct 2006 14:39:30 -0400 | From | Phillip Susi <> | Subject | Re: [Patch 0/5] I/O statistics through request queues |
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Would this be a good candidate to implement using kprobes? I was under the impression that basing instrumentation on kprobes would be a good thing since you can load the instrumentation code only when needed, then unload it.
Martin Peschke wrote: > This patch set makes the block layer maintain statistics for request > queues. Resulting data closely resembles the actual I/O traffic to a > device, as the block layer takes hints from block device drivers when a > request is being issued as well as when it is about to complete. > > It is crucial (for us) to be able to look at such kernel level data in > case of customer situations. It allows us to determine what kind of > requests might be involved in performance situations. This information > helps to understand whether one faces a device issue or a Linux issue. > Not being able to tap into performance data is regarded as a big minus > by some enterprise customers, who are reluctant to use Linux SCSI > support or Linux. > > Statistics data includes: > - request sizes (read + write), > - residual bytes of partially completed requests (read + write), > - request latencies (read + write), > - request retries (read + write), > - request concurrency, > > For sample data please have a look at the SCSI stack patch or the DASD > driver patch respectively. This data is only gathered if statistics have > been enabled by users at run time (default is off). > > The advantage of instrumenting request queues is that we can cover a > broad range of devices, including SCSI tape devices. > Having the block layer maintain such statistics on behalf of drivers > provides for comparability through a common set of statistics. > > A previous approach was to put all the code into the SCSI stack: > http://marc.theaimsgroup.com/?l=linux-kernel&m=115928678420835&w=2 > I gathered from feedback that moving that stuff to the block layer > might be preferable. > > These patches use the statistics component described in > Documentation/statistics.txt. > > Patches are against 2.6.19-rc2-mm2. > > [Patch 1/5] I/O statistics through request queues: timeval_to_us() > [Patch 2/5] I/O statistics through request queues: queue instrumentation > [Patch 3/5] I/O statistics through request queues: small SCSI cleanup > [Patch 4/5] I/O statistics through request queues: SCSI > [Patch 5/5] I/O statistics through request queues: DASD > > Martin >
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