[PATCH 07/10] perf: Optimize perf_output_copy

Peter Zijlstra
2010-05-21T09:11:30Z

[-- Attachment #1: perf-opt-output_copy.patch --]
[-- Type: text/plain, Size: 3047 bytes --]

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>
---
include/linux/perf_event.h | 3 ++
kernel/perf_event.c | 54 +++++++++++++++++++++------------------------
2 files changed, 29 insertions(+), 28 deletions(-)

Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/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;
};
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -2960,39 +2960,30 @@ 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,
@@ -3058,6 +3049,13 @@ int perf_output_begin(struct perf_output
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;