[tip:perf/core] perf: Fix wakeup storm for RO mmap()s
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From: tip-bot for Peter Zijlstra on 21 May 2010 07:40 Commit-ID: adb8e118f288dc4c569ac9a89010b81a4745fbf0 Gitweb: http://git.kernel.org/tip/adb8e118f288dc4c569ac9a89010b81a4745fbf0 Author: Peter Zijlstra <a.p.zijlstra(a)chello.nl> AuthorDate: Thu, 20 May 2010 16:21:55 +0200 Committer: Ingo Molnar <mingo(a)elte.hu> CommitDate: Fri, 21 May 2010 11:37:58 +0200 perf: Fix wakeup storm for RO mmap()s RO mmap()s don't update the tail pointer, so comparing against it for determining the written data size doesn't really do any good. Keep track of when we last did a wakeup, and compare against that. Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl> Cc: Arnaldo Carvalho de Melo <acme(a)redhat.com> Cc: Frederic Weisbecker <fweisbec(a)gmail.com> Cc: Paul Mackerras <paulus(a)samba.org> Cc: Mike Galbraith <efault(a)gmx.de> Cc: Steven Rostedt <rostedt(a)goodmis.org> LKML-Reference: <20100521090710.684479310(a)chello.nl> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- include/linux/perf_event.h | 2 +- kernel/perf_event.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 7cd7b35..7098ebb 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -599,7 +599,7 @@ struct perf_mmap_data { local_t head; /* write position */ local_t nest; /* nested writers */ local_t events; /* event limit */ - local_t wakeup; /* needs a wakeup */ + local_t wakeup; /* wakeup stamp */ local_t lost; /* nr records lost */ long watermark; /* wakeup watermark */ diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 7a93252..1531e0b 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -3056,8 +3056,8 @@ int perf_output_begin(struct perf_output_handle *handle, handle->offset = offset; handle->head = head; - if (head - tail > data->watermark) - local_inc(&data->wakeup); + if (head - local_read(&data->wakeup) > data->watermark) + local_add(data->watermark, &data->wakeup); if (have_lost) { lost_event.header.type = PERF_RECORD_LOST; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |