Messages in this thread | | | Date | Thu, 11 Jun 2009 19:14:36 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 00/11] [GIT PULL] more updates for the tag format |
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On Thu, Jun 11, 2009 at 11:47:51AM -0400, Theodore Tso wrote: > On Thu, Jun 11, 2009 at 09:03:18AM -0400, Christoph Hellwig wrote: > > On Wed, Jun 10, 2009 at 12:03:03PM -0400, Theodore Tso wrote: > > > Yes, another approach for handling this case would be to take my > > > "jbd2_dev_to_name" function and support it as a first-class tagged > > > type; after all, I'm sure ext4 won't be the only place that would like > > > to take a dev_t and print the device name. So this could certainly be > > > fixed by adding some kind of "<dev:xxx>" sort of tagged name. > > > > We should absolutely agree on one way to represent block device for > > tracers. At this point xfs, gfs2 and the block tracer all use > > major/minor. I agree that having a name would be nicer for text output, > > but I really want to keep the dev_t for the binary output. We should > > also make sure we agree on a field name so that filtering will work > > the same for all block-related tracers (especially important if we want > > to trace something from the filesystem down to the block layer). > > And I want to keep the dev_t as what stored in the ring buffer for > space reasons; but the text name is far more convient in terms of > being human-readable, *especially* given there are some crazy people > out there wanting to make major/minor numbers be completely random. > The problem with that is that a log trace file might not be useful > after a reboot, unless someone had enough foresight to save the device > mappings which were in effect at the that the trace was taken. > > So if we store the dev_t in the ring buffer, and have a way of > translating the dev_t into a human-friendly name at printk happen, I > think that meets both of our goals. That would imply that filtering > would be using a device number, which would certainly be more > efficient than doing a string compare. > > - Ted
For the filters, we could enter the text name which would be internally converted into a dev_t, there should be no problem.
Also the raw dev_t can be stored and then human-friendly printed on print time.
Both seem about trivial to add.
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