* Christoph Hellwig ([email protected]) wrote:
> 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.
Or we can use a vprintk-like function to parse the format string and
serialize the information into trace buffers. I prefer this latter
option because, overall, it will localize the probes in a few bytes of
functions instead of duplicating the memory and instruction cache
required by multiple serializing functions.
I have the code ready, but I do not want to flood LKML with patches
neither....
Mathieu
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
