Messages in this thread | | | Date | Thu, 6 Nov 2008 06:14:08 -0800 | From | Arjan van de Ven <> | Subject | Re: [PATCH] ftrace: add an fsync tracer |
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On Thu, 06 Nov 2008 13:55:38 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, 2008-11-05 at 09:49 -0800, Arjan van de Ven wrote: > > From 63c1b869d94eb31a98015af09fb24e22151f2f00 Mon Sep 17 00:00:00 > > 2001 From: Arjan van de Ven <arjan@linux.intel.com> > > Date: Tue, 4 Nov 2008 21:08:11 -0800 > > Subject: [PATCH] ftrace: add an fsync tracer > > > > fsync() (and its cousin, fdatasync()) are important chokepoints in > > the kernel as they imply very expensive operations, both in terms > > of filesystem operations (ext3 writes back its entire journal) as > > well as the block layer (fsync() implies sending a cache flushing > > barrier to the SATA/SCSI disk). > > > > This tracer makes a log of which application calls fsync() on which > > file, so that developers and others interested in finding these > > choke points can locate them and fix them in the apps that call > > this function. > > Sorry, but I have to object to such single purpose tracers.. > > If we go this way we'll end up with a gazillion little tracers, non of > which are really useful. > > Please work on getting something like a syscall tracer, or lttng like > event tracer. >
btw a syscall tracer is not long term right, just like system call level auditing was the wrong thing: you don't have the real information of what's being worked on. having the trace points on the do_FOO() level is the right thing, and that's exactly what my patch does.
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