Messages in this thread | | | Date | Mon, 13 Apr 2009 22:11:55 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] blktrace: move trace/ dir to /sys/block/sda/ |
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* Jens Axboe <jens.axboe@oracle.com> wrote:
> On Mon, Apr 13 2009, Li Zefan wrote: > > Impact: allow ftrace-plugin blktrace to trace device-mapper devices > > > > blktrace can't trace a single partition, so it makes no sense to > > have one trace/ dir in each /sys/block/sda/sdaX. Move it to > > /sys/block/sda/. > > > > Thus we fix an issue reported by Ted, that ftrace-plugin > > blktrace can't be used to trace device-mapper devices. > > Perhaps I never committed that patch, but it would be trivial to > do partition based blktrace tracing. It's also quite useful. So > please don't go changing things to make that harder to support, it > would be nicer to just add the (small) bits to support > per-partition tracing. It's basically just a start/stop sector > range, while some events are per-device and should just be > included always.
btw., per tracepoint filters could be used for that. That would allow multiple partitions to be traced at once.
blktrace user-space could make use of sector range filters straight away [ hm, Tom - do we have the <= comparison operator already, or is that still WIP? ] - but i think it's better to do this in a more integrated way: via the sysfs API, via /sys/block/sda/sda2/trace/.
So when a partition's trace entry is activated, it would auto-install a specific filter expression for sda, with the sector range of that partition. Or something like that. How does this sound?
Ingo
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