Messages in this thread | | | Date | Thu, 30 Aug 2007 18:21:28 +0100 | From | Christoph Hellwig <> | Subject | Re: [patch 4/4] Port of blktrace to the Linux Kernel Markers. |
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On Mon, Aug 27, 2007 at 12:05:44PM -0400, Mathieu Desnoyers wrote: > Here is the first stage of a port of blktrace to the Linux Kernel Markers. The > advantage of this port is that it minimizes the impact on the running when > blktrace is not active. > > A few remarks : this patch has the positive effect of removing some code > from the block io tracing hot paths, minimizing the i-cache impact in a > system where the io tracing is compiled in but inactive. > > It also moves the blk tracing code from a header (and therefore from the > body of the instrumented functions) to a separate C file. > > There, as soon as one device has to be traced, all devices have to > execute the tracing function call when they pass by the instrumentation site. > This is slower than the previous inline function which tested the condition > quickly. > > It does not make the code smaller, since I left all the specialized > tracing functions for requests, bio, generic, remap, which would go away > once a generic infrastructure is in place to serialize the information > passed to the marker. This is mostly why I consider it as a step towards the > full improvements that could bring the markers.
I like this as it moves the whole tracing code out of line. It would be nice if we could make blktrace a module with this, but we'd need to change the interface away from an ioctl on the block device for that.
Btw, something that really shows here and what I noticed in my sputrace aswell is that there is a lot of boilerplate code due to the varargs trace handlers. We really need some way to auto-generate the boilerplate for the trace function to avoid coding this up everywhere. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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