On Tue, Nov 12, 2013 at 12:07:51PM -0300, Arnaldo Carvalho de Melo wrote: > Em Tue, Nov 12, 2013 at 03:57:07PM +0100, Peter Zijlstra escreveu: > > On Tue, Nov 12, 2013 at 07:46:56AM -0700, David Ahern wrote: > > > When recording raw_syscalls for the entire system, e.g., > > > perf record -e raw_syscalls:*,sched:sched_switch -a -- sleep 1 > > > > > > you end up with a negative feedback loop as perf itself calls write() > > > fairly > > > often. This patch handles the problem by mmap'ing the file in chunks of > > > 64M at > > > a time and copies events from the event buffers to the file avoiding write > > > system calls. > > > > You know this completely fails the moment you trace faults, because > > every new access to one of those pages (to mark it dirty) will trigger a > > fault. And we'll take a bunch more faults -- one for each page -- than > > we ever did write() syscalls. > > So we should provide a neon lettered warning when doing that, no? :-)
Dunno.. it _should_ all work. Try it and see what it does.. Once the events are bigger than a page things might get 'interesting' though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
