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linux-next/kernel/events
Peter Zijlstra 91a612eea9 perf/core: Fix dynamic interrupt throttle
There were two problems with the dynamic interrupt throttle mechanism,
both triggered by the same action.

When you (or perf_fuzzer) write a huge value into
/proc/sys/kernel/perf_event_max_sample_rate the computed
perf_sample_allowed_ns becomes 0. This effectively disables the whole
dynamic throttle.

This is fixed by ensuring update_perf_cpu_limits() never sets the
value to 0. However, we allow disabling of the dynamic throttle by
writing 100 to /proc/sys/kernel/perf_cpu_time_max_percent. This will
generate a warning in dmesg.

The second problem is that by setting the max_sample_rate to a huge
number, the adaptive process can take a few tries, since it halfs the
limit each time. Change that to directly compute a new value based on
the observed duration.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-03-21 09:08:17 +01:00
..
callchain.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
core.c perf/core: Fix dynamic interrupt throttle 2016-03-21 09:08:17 +01:00
hw_breakpoint.c perf: Collapse and fix event_function_call() users 2016-01-21 18:54:24 +01:00
internal.h perf: Fix AUX buffer refcounting 2015-07-06 14:08:30 +02:00
Makefile ftrace: allow architectures to specify ftrace compile options 2015-01-29 09:19:19 +01:00
ring_buffer.c perf: Synchronously free aux pages in case of allocation failure 2016-01-21 18:54:27 +01:00
uprobes.c uprobes: __create_xol_area() must nullify xol_mapping.fault 2016-02-29 08:47:51 +01:00