What follows are some notes I made when I last got PAPI working on Linux.

== Installing PAPI ==

 * Grab PAPI and the most recent perfctr 2.6.x
 * Unpack both under `~/tmp`

=== On Ubuntu ===

Get the bits needed to build a kernel:

 * `sudo apt-get install linux-kernel-devel fakeroot kernel-wedge kernel-package`
 * `sudo apt-get build-dep linux-source`
 * `sudo apt-get install linux-source`
 * This seems to get a slightly out-of-date version, but maybe that's ok

Unpack and patch the kernel:

 * `cd ~/tmp`
 * {{{tar xvjf /usr/src/linux-source-*}}}
 * `cd linux-source*`
 * Read `$perfctr/INSTALL`
 * `$perfctr/update-kernel` Might fail because it can't find the right patch, in which case:
 * `$perfctr/update-kernel --patch=2.6.22` (tell it which patch)
 * `make menuconfig`
 * Turn on `perfctr`-related stuff under "Processor type and features", "Performance-monitoring counters support".
   You need both "virtual" and "global" support turned on.

Build the kernel:

 * {{{make-kpkg --rootcmd fakeroot --initrd --append-to-version=-perfctr kernel-image kernel-headers}}}
 * wait a while

Install the kernel:

 * `cd ..`
 * `dpkg -i linux-image-*.deb`
 * `dpkg -i linux-headers-*.deb`
 * Copy contents of `lib/firmware/$old_kernel` to `/lib/firmware/$new_kernel` (not sure if this is right, but so
   far the wireless adaptor still seems fine under the new kernel, so I guess it worked)
 * `cd $perfctr`
 * {{{cp etc/perfctr.rules /etc/udev/rules.d/99-perfctr.rules}}}
 * Boot the new kernel
 * I seemed to have `perfctr` built as a module, probably selected that in menuconfig by mistake, so anyway:
 * `sudo modprobe perfctr`
 * {{{cat /proc/misc | grep perfctr}}} should now show perfctr, and you should have `/dev/perfctr`.

Build the perfctr library:

 * `cd $perfctr`
 * `make PREFIX=$HOME/local`
 * `make PREFIX=$HOME/local install`

Now to build PAPI:

 * `cd $papi`
 * The configure script had some trouble detecting the C compiler for me, I had to edit the configure script and re-autoconf it.   Change
{{{
if test "$OS" != "linux"; then
  ...
else
  AC_PROG_CC
  AC_PROG_F77
fi
}}}
to
{{{
AC_PROG_CC
AC_PROG_F77
}}}

 * `autoconf`  
 * We have a choice about whether to use the `libperfctr` in the PAPI distribution, or the one that comes with `perfctr`.  The
   latter is probably more correct, but the former also worked for me.
 * `./configure --with-perfctr-prefix=$HOME/local` --prefix=$HOME/local
 * `make`
 * `./run-tests.sh` (I got about 4 failures on Core 2)
 * `make install`

Now it's all built, with header files in `$HOME/local/include`, libraries in `$HOME/local/lib`.