On Wed, 2010-11-03 at 20:29 +0100, Jakub Jelinek wrote: > > It seems like if it was that easy, it would have happened and we'd have > > a solution in the upstream kernel... > > I think we had one in the upstream kernel for some time, then Linus just > didn't like to see it needing too many bugfixes needed for it and nuked it. [..] > > (One thing that definitely makes things tricky is paging in debuginfo. I > > think I saw a discussion somewhere that systemtap preemptively was > > paging in all debuginfo for traced modules. That's tricky in systemwide > > Yeah, systemtap does that (and has that in kernel unwinder for userspace). Looking at systemstap, they are exploiting the fact that they already have an infrastructure for compiling arbitrary code into modules and loading it into the kernel. So they've entirely bypassed the question of how to get a DWARF unwinder upstream into the kernel. Of course, any profiling framework *could* work with a custom kernel module, but sysprof was actually kicked out of Fedora for a while because it had a much simpler not-in-the-kernel module. It now uses upstream hooks. So systemtap at best answers the technical questions, and not the practical question of actually making something happen. If the earlier experience was a DWARF one got in, then got removed, it's a little hard for me to see how a DWARF unwinder in the kernel is a practical direction. Maybe I should have headed down earlier this week and picketed outside the Kernel summit... - Owen -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
