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perf_counter: Subtract the buffer size field from the event record size

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We compute the perf raw sample size by aligning the raw ftrace
event size plus the buffer size field itself. We do that
instead of aligning only the perf raw sample size, so that we
might economize some in some cases.

But this buffer size field is not stored in the perf raw
sample, we must then substract its size from the buffer once we
computed the alignment unless we may get a useless u32 field in
the buffer.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090810141129.GA5124@nowhere>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2009-08-10 16:11:32 +02:00 committed by Ingo Molnar
parent a4e95fc2cb
commit 304703aba3
1 changed files with 7 additions and 1 deletions
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8
include/trace/ftrace.h
View file

@ -637,7 +637,12 @@ __attribute__((section("_ftrace_events"))) event_##call = { \
* pc = preempt_count();
*
* __data_size = ftrace_get_offsets_<call>(&__data_offsets, args);
* __entry_size = __data_size + sizeof(*entry);
*
* // Below we want to get the aligned size by taking into account
* // the u32 field that will later store the buffer size
* __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),
* sizeof(u64));
* __entry_size -= sizeof(u32);
*
* do {
* char raw_data[__entry_size]; <- allocate our sample in the stack
@ -687,6 +692,7 @@ static void ftrace_profile_##call(proto) \
__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
sizeof(u64)); \
__entry_size -= sizeof(u32); \
\
do { \
char raw_data[__entry_size]; \