readahead: add trace points

Add a couple of trace points to make debugging readahead logic easier.

Link: https://lkml.kernel.org/r/20250908145533.31528-2-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/trace/events/readahead.h b/include/trace/events/readahead.h
new file mode 100644 (file)
index 0000000..992a6ce
--- /dev/null
+++ b/include/trace/events/readahead.h
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM readahead
+
+#if !defined(_TRACE_FILEMAP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_READAHEAD_H
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+
+TRACE_EVENT(do_page_cache_ra,
+       TP_PROTO(struct inode *inode, pgoff_t index, unsigned long nr_to_read,
+                unsigned long lookahead_size),
+
+       TP_ARGS(inode, index, nr_to_read, lookahead_size),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, i_ino)
+               __field(dev_t, s_dev)
+               __field(pgoff_t, index)
+               __field(unsigned long, nr_to_read)
+               __field(unsigned long, lookahead_size)
+       ),
+
+       TP_fast_assign(
+               __entry->i_ino = inode->i_ino;
+               __entry->s_dev = inode->i_sb->s_dev;
+               __entry->index = index;
+               __entry->nr_to_read = nr_to_read;
+               __entry->lookahead_size = lookahead_size;
+       ),
+
+       TP_printk(
+               "dev=%d:%d ino=%lx index=%lu nr_to_read=%lu lookahead_size=%lu",
+               MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+               __entry->index, __entry->nr_to_read, __entry->lookahead_size
+       )
+);
+
+TRACE_EVENT(page_cache_ra_order,
+       TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra),
+
+       TP_ARGS(inode, index, ra),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, i_ino)
+               __field(dev_t, s_dev)
+               __field(pgoff_t, index)
+               __field(unsigned int, order)
+               __field(unsigned int, size)
+               __field(unsigned int, async_size)
+               __field(unsigned int, ra_pages)
+       ),
+
+       TP_fast_assign(
+               __entry->i_ino = inode->i_ino;
+               __entry->s_dev = inode->i_sb->s_dev;
+               __entry->index = index;
+               __entry->order = ra->order;
+               __entry->size = ra->size;
+               __entry->async_size = ra->async_size;
+               __entry->ra_pages = ra->ra_pages;
+       ),
+
+       TP_printk(
+               "dev=%d:%d ino=%lx index=%lu order=%u size=%u async_size=%u ra_pages=%u",
+               MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+               __entry->index, __entry->order, __entry->size,
+               __entry->async_size, __entry->ra_pages
+       )
+);
+
+DECLARE_EVENT_CLASS(page_cache_ra_op,
+       TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+                unsigned long req_count),
+
+       TP_ARGS(inode, index, ra, req_count),
+
+       TP_STRUCT__entry(
+               __field(unsigned long, i_ino)
+               __field(dev_t, s_dev)
+               __field(pgoff_t, index)
+               __field(unsigned int, order)
+               __field(unsigned int, size)
+               __field(unsigned int, async_size)
+               __field(unsigned int, ra_pages)
+               __field(unsigned int, mmap_miss)
+               __field(loff_t, prev_pos)
+               __field(unsigned long, req_count)
+       ),
+
+       TP_fast_assign(
+               __entry->i_ino = inode->i_ino;
+               __entry->s_dev = inode->i_sb->s_dev;
+               __entry->index = index;
+               __entry->order = ra->order;
+               __entry->size = ra->size;
+               __entry->async_size = ra->async_size;
+               __entry->ra_pages = ra->ra_pages;
+               __entry->mmap_miss = ra->mmap_miss;
+               __entry->prev_pos = ra->prev_pos;
+               __entry->req_count = req_count;
+       ),
+
+       TP_printk(
+               "dev=%d:%d ino=%lx index=%lu req_count=%lu order=%u size=%u async_size=%u ra_pages=%u mmap_miss=%u prev_pos=%lld",
+               MAJOR(__entry->s_dev), MINOR(__entry->s_dev), __entry->i_ino,
+               __entry->index, __entry->req_count, __entry->order,
+               __entry->size, __entry->async_size, __entry->ra_pages,
+               __entry->mmap_miss, __entry->prev_pos
+       )
+);
+
+DEFINE_EVENT(page_cache_ra_op, page_cache_sync_ra,
+       TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+                unsigned long req_count),
+       TP_ARGS(inode, index, ra, req_count)
+);
+
+DEFINE_EVENT(page_cache_ra_op, page_cache_async_ra,
+       TP_PROTO(struct inode *inode, pgoff_t index, struct file_ra_state *ra,
+                unsigned long req_count),
+       TP_ARGS(inode, index, ra, req_count)
+);
+
+#endif /* _TRACE_FILEMAP_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

diff --git a/mm/readahead.c b/mm/readahead.c
index 406756d343092fb1ce6a868facfcc9f92379fd2d..210395fe104474ceb5a8806ad742719eaaeb687b 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -129,6 +129,9 @@
 #include <linux/fadvise.h>
 #include <linux/sched/mm.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/readahead.h>
+
 #include "internal.h"
 
 /*
@@ -314,6 +317,7 @@ static void do_page_cache_ra(struct readahead_control *ractl,
        loff_t isize = i_size_read(inode);
        pgoff_t end_index;      /* The last page we want to read */
 
+       trace_do_page_cache_ra(inode, index, nr_to_read, lookahead_size);
        if (isize == 0)
                return;
 
@@ -470,6 +474,7 @@ void page_cache_ra_order(struct readahead_control *ractl,
        gfp_t gfp = readahead_gfp_mask(mapping);
        unsigned int new_order = ra->order;
 
+       trace_page_cache_ra_order(mapping->host, start, ra);
        if (!mapping_large_folio_support(mapping)) {
                ra->order = 0;
                goto fallback;
@@ -554,6 +559,7 @@ void page_cache_sync_ra(struct readahead_control *ractl,
        unsigned long max_pages, contig_count;
        pgoff_t prev_index, miss;
 
+       trace_page_cache_sync_ra(ractl->mapping->host, index, ra, req_count);
        /*
         * Even if readahead is disabled, issue this request as readahead
         * as we'll need it to satisfy the requested range. The forced
@@ -638,6 +644,7 @@ void page_cache_async_ra(struct readahead_control *ractl,
        if (folio_test_writeback(folio))
                return;
 
+       trace_page_cache_async_ra(ractl->mapping->host, index, ra, req_count);
        folio_clear_readahead(folio);
 
        if (blk_cgroup_congested())