Michael Neuling <mi...@neuling.org> wrote: > Frederic Weisbecker <fweis...@gmail.com> wrote: > > > On Thu, Aug 16, 2012 at 02:23:54PM +1000, Michael Neuling wrote: > > > Hi, > > > > > > I've been trying to get hardware breakpoints with perf to work on POWER7 > > > but I'm getting the following: > > > > > > % perf record -e mem:0x10000000 true > > > > > > Error: sys_perf_event_open() syscall returned with 28 (No space left > > > on device). /bin/dmesg may provide additional information. > > > > > > Fatal: No CONFIG_PERF_EVENTS=y kernel support configured? > > > > > > true: Terminated > > > > > > (FWIW adding -a and it works fine) > > > > > > Debugging it seems that __reserve_bp_slot() is returning ENOSPC because > > > it thinks there are no free breakpoint slots on this CPU. > > > > > > I have a 2 CPUs, so perf userspace is doing two perf_event_open syscalls > > > to add a counter to each CPU [1]. The first syscall succeeds but the > > > second is failing. > > > > > > On this second syscall, fetch_bp_busy_slots() sets slots.pinned to be 1, > > > despite there being no breakpoint on this CPU. This is because the call > > > the task_bp_pinned, checks all CPUs, rather than just the current CPU. > > > POWER7 only has one hardware breakpoint per CPU (ie. HBP_NUM=1), so we > > > return ENOSPC. > > > > > > The following patch fixes this by checking the associated CPU for each > > > breakpoint in task_bp_pinned. I'm not familiar with this code, so it's > > > provided as a reference to the above issue. > > > > > > Mikey > > > > > > 1. not sure why it doesn't just do one syscall and specify all CPUs, but > > > that's another issue. Using two syscalls should work. > > > > This patch seems to make sense. I'll try it and run some tests. > > Can I have your Signed-off-by ?
Frederic, Did you ever get to testing or integrating this patch? Mikey > Of course... > > Signed-off-by: Michael Neuling <mi...@neuling.org> _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
