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>

1 files changed, 26 insertions, 28 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 1531e0b409a5..b67549a08626 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;