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>

diff --git a/include/trace/events/filemap.h b/include/trace/events/filemap.h
new file mode 100644 (file)
index 0000000..2d36386
--- /dev/null
+++ b/include/trace/events/filemap.h
@@ -0,0 +1,79 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM filemap
+
+#if !defined(_TRACE_FILEMAP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FILEMAP_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/device.h>
+#include <linux/kdev_t.h>
+
+TRACE_EVENT(mm_filemap_delete_from_page_cache,
+
+       TP_PROTO(struct page *page),
+
+       TP_ARGS(page),
+
+       TP_STRUCT__entry(
+               __field(struct page *, page)
+               __field(unsigned long, i_ino)
+               __field(unsigned long, index)
+               __field(dev_t, s_dev)
+       ),
+
+       TP_fast_assign(
+               __entry->page = page;
+               __entry->i_ino = page->mapping->host->i_ino;
+               __entry->index = page->index;
+               if (page->mapping->host->i_sb)
+                       __entry->s_dev = page->mapping->host->i_sb->s_dev;
+               else
+                       __entry->s_dev = page->mapping->host->i_rdev;
+       ),
+
+       TP_printk("dev %d:%d ino %lx page=%p pfn=%lu ofs=%lu",
+               MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+               __entry->i_ino,
+               __entry->page,
+               page_to_pfn(__entry->page),
+               __entry->index << PAGE_SHIFT)
+);
+
+TRACE_EVENT(mm_filemap_add_to_page_cache,
+
+       TP_PROTO(struct page *page),
+
+       TP_ARGS(page),
+
+       TP_STRUCT__entry(
+               __field(struct page *, page)
+               __field(unsigned long, i_ino)
+               __field(unsigned long, index)
+               __field(dev_t, s_dev)
+       ),
+
+       TP_fast_assign(
+               __entry->page = page;
+               __entry->i_ino = page->mapping->host->i_ino;
+               __entry->index = page->index;
+               if (page->mapping->host->i_sb)
+                       __entry->s_dev = page->mapping->host->i_sb->s_dev;
+               else
+                       __entry->s_dev = page->mapping->host->i_rdev;
+       ),
+
+       TP_printk("dev %d:%d ino %lx page=%p pfn=%lu ofs=%lu",
+               MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
+               __entry->i_ino,
+               __entry->page,
+               page_to_pfn(__entry->page),
+               __entry->index << PAGE_SHIFT)
+);
+
+#endif /* _TRACE_FILEMAP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

diff --git a/mm/filemap.c b/mm/filemap.c
index cbde8842a37458ec87f6fef57c7cadd59c8b98e1..9824c8af6004231abf6e275427389342f799bfb4 100644 (file)
--- 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
@@ -463,6 +467,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                if (likely(!error)) {
                        mapping->nrpages++;
                        __inc_zone_page_state(page, NR_FILE_PAGES);
+                       trace_mm_filemap_add_to_page_cache(page);
                        spin_unlock_irq(&mapping->tree_lock);
                } else {
                        page->mapping = NULL;