mm: trace filemap add and del

Use the events API to trace filemap loading and unloading of file pieces
into the page cache.

This patch aims at tracing the eviction reload cycle of executable and
shared libraries pages in a memory constrained environment.

The typical usage is to spot a specific device and inode (for example
/lib/libc.so) to see the eviction cycles, and find out if frequently
used code is rather spread across many pages (bad) or coallesced (good).

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index e1979fdca805..2581826409f2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -35,6 +35,9 @@
 #include <linux/cleancache.h>
 #include "internal.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/filemap.h>
+
 /*
  * FIXME: remove all knowledge of the buffer layer from the core VM
  */
@@ -113,6 +116,7 @@ void __delete_from_page_cache(struct page *page)
 {
         struct address_space *mapping = page->mapping;
 
+        trace_mm_filemap_delete_from_page_cache(page);
         /*
          * if we're uptodate, flush out into the cleancache, otherwise
          * invalidate any existing cleancache entries.  We can't leave
@@ -464,6 +468,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                         mapping->nrpages++;
                         __inc_zone_page_state(page, NR_FILE_PAGES);
                         spin_unlock_irq(&mapping->tree_lock);
+                        trace_mm_filemap_add_to_page_cache(page);
                 } else {
                         page->mapping = NULL;
                         /* Leave page->index set: truncation relies upon it */