[PATCH 1/2] xfs: add tracepoints to readpage calls

[Dave Chinner <david@xxxxxxxxxxxxx>]

From: Dave Chinner <dchinner@xxxxxxxxxx>

This allows us to see page cache driven readahead in action as it
passes through XFS. This helps to understand buffered read
throughput problems such as readahead IO IO sizes being too small
for the underlying device to reach max throughput.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/xfs_aops.c  |  2 ++
 fs/xfs/xfs_trace.h | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 29e7e5d..379c089 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1917,6 +1917,7 @@ xfs_vm_readpage(
        struct file             *unused,
        struct page             *page)
 {
+       trace_xfs_vm_readpage(page->mapping->host, 1);
        return mpage_readpage(page, xfs_get_blocks);
 }
 
@@ -1927,6 +1928,7 @@ xfs_vm_readpages(
        struct list_head        *pages,
        unsigned                nr_pages)
 {
+       trace_xfs_vm_readpages(mapping->host, nr_pages);
        return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);
 }
 
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 877079eb..391d797 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -1222,6 +1222,32 @@ DEFINE_PAGE_EVENT(xfs_writepage);
 DEFINE_PAGE_EVENT(xfs_releasepage);
 DEFINE_PAGE_EVENT(xfs_invalidatepage);
 
+DECLARE_EVENT_CLASS(xfs_readpage_class,
+       TP_PROTO(struct inode *inode, int nr_pages),
+       TP_ARGS(inode, nr_pages),
+       TP_STRUCT__entry(
+               __field(dev_t, dev)
+               __field(xfs_ino_t, ino)
+               __field(int, nr_pages)
+       ),
+       TP_fast_assign(
+               __entry->dev = inode->i_sb->s_dev;
+               __entry->ino = inode->i_ino;
+               __entry->nr_pages = nr_pages;
+       ),
+       TP_printk("dev %d:%d ino 0x%llx nr_pages %d",
+                 MAJOR(__entry->dev), MINOR(__entry->dev),
+                 __entry->ino,
+                 __entry->nr_pages)
+)
+
+#define DEFINE_READPAGE_EVENT(name)            \
+DEFINE_EVENT(xfs_readpage_class, name, \
+       TP_PROTO(struct inode *inode, int nr_pages), \
+       TP_ARGS(inode, nr_pages))
+DEFINE_READPAGE_EVENT(xfs_vm_readpage);
+DEFINE_READPAGE_EVENT(xfs_vm_readpages);
+
 DECLARE_EVENT_CLASS(xfs_imap_class,
        TP_PROTO(struct xfs_inode *ip, xfs_off_t offset, ssize_t count,
                 int type, struct xfs_bmbt_irec *irec),
-- 
2.5.0