From adb8e118f288dc4c569ac9a89010b81a4745fbf0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 20 May 2010 16:21:55 +0200 Subject: [PATCH] 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 Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: Paul Mackerras Cc: Mike Galbraith Cc: Steven Rostedt LKML-Reference: <20100521090710.684479310@chello.nl> Signed-off-by: Ingo Molnar --- 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 7cd7b356447d..7098ebbb3b3a 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 7a932526946f..1531e0b409a5 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; -- 2.20.1