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>

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 7098ebb..7bd17f0 100644 (file)
--- 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 (file)
--- 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;