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Subject[tip:perf/core] perf: Optimize perf_output_copy()
Commit-ID:  5d967a8be636a4f301a8daad642bd1007299d9ec
Gitweb: http://git.kernel.org/tip/5d967a8be636a4f301a8daad642bd1007299d9ec
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 20 May 2010 16:46:39 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 21 May 2010 11:37:59 +0200

perf: Optimize perf_output_copy()

Reduce the clutter in perf_output_copy() by keeping
an interator in perf_output_handle.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100521090710.742809176@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/perf_event.h | 3 ++
kernel/perf_event.c | 54 +++++++++++++++++++++----------------------
2 files changed, 29 insertions(+), 28 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 7098ebb..7bd17f0 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -806,6 +806,9 @@ struct perf_output_handle {
unsigned long head;
unsigned long offset;
unsigned long wakeup;
+ unsigned long size;
+ void *addr;
+ int page;
int nmi;
int sample;
};
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 1531e0b..b67549a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2961,39 +2961,30 @@ again:
void perf_output_copy(struct perf_output_handle *handle,
const void *buf, unsigned int len)
{
- unsigned int pages_mask;
- unsigned long offset;
- unsigned int size;
- void **pages;
-
- offset = handle->offset;
- pages_mask = handle->data->nr_pages - 1;
- pages = handle->data->data_pages;
-
- do {
- unsigned long page_offset;
- unsigned long page_size;
- int nr;
-
- nr = (offset >> PAGE_SHIFT) & pages_mask;
- page_size = 1UL << (handle->data->data_order + PAGE_SHIFT);
- page_offset = offset & (page_size - 1);
- size = min_t(unsigned int, page_size - page_offset, len);
-
- memcpy(pages[nr] + page_offset, buf, size);
-
- len -= size;
- buf += size;
- offset += size;
- } while (len);
-
- handle->offset = offset;
+ handle->offset += len;

/*
* Check we didn't copy past our reservation window, taking the
* possible unsigned int wrap into account.
*/
- WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0);
+ if (WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0))
+ return;
+
+ do {
+ unsigned long size = min(handle->size, len);
+
+ memcpy(handle->addr, buf, size);
+
+ len -= size;
+ handle->addr += size;
+ handle->size -= size;
+ if (!handle->size) {
+ handle->page++;
+ handle->page &= handle->data->nr_pages - 1;
+ handle->addr = handle->data->data_pages[handle->page];
+ handle->size = PAGE_SIZE << handle->data->data_order;
+ }
+ } while (len);
}

int perf_output_begin(struct perf_output_handle *handle,
@@ -3059,6 +3050,13 @@ int perf_output_begin(struct perf_output_handle *handle,
if (head - local_read(&data->wakeup) > data->watermark)
local_add(data->watermark, &data->wakeup);

+ handle->page = handle->offset >> (PAGE_SHIFT + data->data_order);
+ handle->page &= data->nr_pages - 1;
+ handle->size = handle->offset & ((PAGE_SIZE << data->data_order) - 1);
+ handle->addr = data->data_pages[handle->page];
+ handle->addr += handle->size;
+ handle->size = (PAGE_SIZE << data->data_order) - handle->size;
+
if (have_lost) {
lost_event.header.type = PERF_RECORD_LOST;
lost_event.header.misc = 0;

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