* Sam Ben <sam.bennn@xxxxxxxxx> wrote: > On 07/12/2013 04:53 PM, Ingo Molnar wrote: > >* Borislav Petkov <bp@xxxxxxxxx> wrote: > > > >>On Fri, Jul 12, 2013 at 10:27:56AM +0200, Ingo Molnar wrote: > >>>Robert Richter and Boris Petkov are working on 'persistent events' > >>>support for perf, which will eventually allow boot time profiling - > >>>I'm not sure if the patches and the tooling support is ready enough > >>>yet for your purposes. > >>Nope, not yet but we're getting there. > >> > >>>Robert, Boris, the following workflow would be pretty intuitive: > >>> > >>> - kernel developer sets boot flag: perf=boot,freq=1khz,size=16MB > >>What does perf=boot mean? I assume boot tracing. > >In this case it would mean boot profiling - i.e. a cycles hardware-PMU > >event collecting into a perf trace buffer as usual. > > > >Essentially a 'perf record -a' work-alike, just one that gets activated as > >early as practical, and which would allow the profiling of memory > >initialization. > > > >Now, one extra complication here is that to be able to profile buddy > >allocator this persistent event would have to work before the buddy > >allocator is active :-/ So this sort of profiling would have to use > >memblock_alloc(). > > Could perf=boot be used to sample the performance of memblock subsystem? > I think the perf subsystem is too late to be initialized and monitor > this. Yes, that would be a useful facility as well, for things with many events were printk is not necessarily practical. Any tracepoint could be utilized. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>