On Tuesday 07 December 2010 13:47:43 Steven Rostedt wrote: > On Tue, 2010-12-07 at 00:03 +0100, Arnd Bergmann wrote: > > > > > yaffs_trace(YAFFS_TRACE_BUFFERS, > > > > > "Out of temp buffers at line %d, other held by lines:",line_no); > > > > > for (i = 0; i < YAFFS_N_TEMP_BUFFERS; i++) > > > > > yaffs_trace(YAFFS_TRACE_BUFFERS," %d ", dev->temp_buffer[i].line); > > > > > yaffs_trace(YAFFS_TRACE_BUFFERS, "\n"); > > > > > > > > > > Would that be OK? > > > > > > > > > > I am loath to have to pull out useful code then plug it back in > > > > > again. > > > > > > > > I don't think the yaffs_trace() function would be much better than > > > > the T() macro, I was talking more about the fact that you have your > > > > own nonstandard tracing infrastructure than the ugliness of the > > > > interface. > > > > > > > > The point of pulling it out now would be force you to rethink the > > > > tracing. If you think that you'd arrive at the same conclusion, just > > > > save the diff between the code with and without tracing so you can > > > > submit that patch again later. > > > > > > > > Having some sort of tracing is clearly useful, but it's also not > > > > essential for the basic yaffs2 operation. We want to keep a > > > > consistent way of presenting trace points across the kernel, so as > > > > long as you do it differently, your code is going to be viewed with > > > > some suspicion. > > > > > > > > Please have a look at how ext4, gfs2 and xfs do tracing. > > > > > > Looking in Linus' tree, all of those contain custom tracing of the form > > > I propose. > > > > Hmm, yes I guess that's right... > > > > I was specifically talking about the include/trace/* based trace events > > as something to look at, not the random printk based tracing stuff. > > Maybe Steven or Frederic can give some more insight on that. > > What are all those T() functions? Some look like they should be replaced > with printk(KERN_* "") functions, some others for tracing (I guess the > ones with YAFFS_TRACE_TRACING). Yes those are very ugly. That is why I proposed changing them to yaffs_trace(bit, "format", args). That gives printk tracing which I can select on the fly by enabling the selected bits in the bitmask. eg. If I want to see the OS calls and the mtd accesses then I enable YAFFS_TRACE_MTD and YAFFS_TRACE_OS and only those grace groups get spat out. People find this very handy, especially during system integration, so I am loath to lose it. It is simple and it works. Will it not be acceptable to just leave in the printk-style messages and perhaps addTRACE_EVENT later? > > ext4, gfs and xfs all have converted to the TRACE_EVENT() methods. When > you have this, you get tracing for free. The work with both ftrace and > perf. You can look at the samples/trace_events/ code for examples. > > Note, if you use TRACE_EVENT() and you want to debug even more, you can > simply add trace_printk() and that will also appear in your tracing > output. >From what I see, ext4 uses both trace_event and wrapped printk tracing, some right alongside eachother so it is a duplication - not a replacement. YAFFS has approx 500 trace lines in it. Some of those would make sense to attach to TRACE_EVENT() , but most not. trace/events/ext4.h has 1172 lines for around 28 events (== 40-odd lines per event). Still reading everything I can find on this (inc, your LWN articles) to get an understanding of what capabilities these give me and what heuristic should be used to define trace points vs printks. -- Charles -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
