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Message-ID: <20240128142522.1524741-1-ming.lei@redhat.com>
Date: Sun, 28 Jan 2024 22:25:22 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
Ming Lei <ming.lei@...hat.com>,
Mike Snitzer <snitzer@...nel.org>,
Don Dutile <ddutile@...hat.com>,
Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Subject: [RFC PATCH] mm/readahead: readahead aggressively if read drops in willneed range
Since commit 6d2be915e589 ("mm/readahead.c: fix readahead failure for
memoryless NUMA nodes and limit readahead max_pages"), ADV_WILLNEED
only tries to readahead 512 pages, and the remained part in the advised
range fallback on normal readahead.
If bdi->ra_pages is set as small, readahead will perform not efficient
enough. Increasing read ahead may not be an option since workload may
have mixed random and sequential I/O.
Improve this situation by maintaining one willneed range maple tree, if
read drops in any willneed range, readahead aggressively just like
what we did before commit 6d2be915e589.
Cc: Mike Snitzer <snitzer@...nel.org>
Cc: Don Dutile <ddutile@...hat.com>
Cc: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
fs/file_table.c | 10 ++++++++++
include/linux/fs.h | 15 +++++++++++++++
mm/filemap.c | 5 ++++-
mm/internal.h | 7 ++++++-
mm/readahead.c | 32 +++++++++++++++++++++++++++++++-
5 files changed, 66 insertions(+), 3 deletions(-)
diff --git a/fs/file_table.c b/fs/file_table.c
index b991f90571b4..bb0303683305 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -61,8 +61,18 @@ struct path *backing_file_user_path(struct file *f)
}
EXPORT_SYMBOL_GPL(backing_file_user_path);
+static inline void file_ra_free(struct file_ra_state *ra)
+{
+ if (ra->need_mt) {
+ mtree_destroy(ra->need_mt);
+ kfree(ra->need_mt);
+ ra->need_mt = NULL;
+ }
+}
+
static inline void file_free(struct file *f)
{
+ file_ra_free(&f->f_ra);
security_file_free(f);
if (likely(!(f->f_mode & FMODE_NOACCOUNT)))
percpu_counter_dec(&nr_files);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed5966a70495..bdbd16990072 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -43,6 +43,7 @@
#include <linux/cred.h>
#include <linux/mnt_idmapping.h>
#include <linux/slab.h>
+#include <linux/maple_tree.h>
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -961,6 +962,7 @@ struct fown_struct {
* @ra_pages: Maximum size of a readahead request, copied from the bdi.
* @mmap_miss: How many mmap accesses missed in the page cache.
* @prev_pos: The last byte in the most recent read request.
+ * @need_mt: maple tree for tracking WILL_NEED ranges
*
* When this structure is passed to ->readahead(), the "most recent"
* readahead means the current readahead.
@@ -972,6 +974,7 @@ struct file_ra_state {
unsigned int ra_pages;
unsigned int mmap_miss;
loff_t prev_pos;
+ struct maple_tree *need_mt;
};
/*
@@ -983,6 +986,18 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
index < ra->start + ra->size);
}
+/*
+ * Check if @index falls in the madvise/fadvise WILLNEED window.
+ */
+static inline bool ra_index_in_need_range(struct file_ra_state *ra,
+ pgoff_t index)
+{
+ if (ra->need_mt)
+ return mtree_load(ra->need_mt, index) != NULL;
+
+ return false;
+}
+
/*
* f_{lock,count,pos_lock} members can be highly contended and share
* the same cacheline. f_{lock,mode} are very frequently used together
diff --git a/mm/filemap.c b/mm/filemap.c
index 750e779c23db..0ffe63d58421 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3147,7 +3147,10 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
*/
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
- ra->size = ra->ra_pages;
+ if (ra_index_in_need_range(ra, vmf->pgoff))
+ ra->size = inode_to_bdi(mapping->host)->io_pages;
+ else
+ ra->size = ra->ra_pages;
ra->async_size = ra->ra_pages / 4;
ractl._index = ra->start;
page_cache_ra_order(&ractl, ra, 0);
diff --git a/mm/internal.h b/mm/internal.h
index f309a010d50f..17bd970ff23c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -120,13 +120,18 @@ void unmap_page_range(struct mmu_gather *tlb,
unsigned long addr, unsigned long end,
struct zap_details *details);
+void file_ra_add_need_range(struct file_ra_state *ra, pgoff_t start,
+ pgoff_t end);
void page_cache_ra_order(struct readahead_control *, struct file_ra_state *,
unsigned int order);
void force_page_cache_ra(struct readahead_control *, unsigned long nr);
static inline void force_page_cache_readahead(struct address_space *mapping,
struct file *file, pgoff_t index, unsigned long nr_to_read)
{
- DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, index);
+ struct file_ra_state *ra = &file->f_ra;
+ DEFINE_READAHEAD(ractl, file, ra, mapping, index);
+
+ file_ra_add_need_range(ra, index, index + nr_to_read);
force_page_cache_ra(&ractl, nr_to_read);
}
diff --git a/mm/readahead.c b/mm/readahead.c
index 23620c57c122..0882ceecf9ff 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -140,9 +140,38 @@ file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
{
ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
ra->prev_pos = -1;
+ ra->need_mt = NULL;
}
EXPORT_SYMBOL_GPL(file_ra_state_init);
+static void file_ra_setup_need_mt(struct file_ra_state *ra)
+{
+ struct maple_tree *mt = kzalloc(sizeof(*mt), GFP_KERNEL);
+
+ if (!mt)
+ return;
+
+ mt_init(mt);
+ if (cmpxchg(&ra->need_mt, NULL, mt) != NULL)
+ kfree(mt);
+}
+
+/* Maintain one willneed range hint for speedup readahead */
+void file_ra_add_need_range(struct file_ra_state *ra, pgoff_t start,
+ pgoff_t end)
+{
+ /* ignore small willneed range */
+ if (end - start < 4 * ra->ra_pages)
+ return;
+
+ if (!ra->need_mt)
+ file_ra_setup_need_mt(ra);
+
+ if (ra->need_mt)
+ mtree_insert_range(ra->need_mt, start, end, (void *)1,
+ GFP_KERNEL);
+}
+
static void read_pages(struct readahead_control *rac)
{
const struct address_space_operations *aops = rac->mapping->a_ops;
@@ -552,9 +581,10 @@ static void ondemand_readahead(struct readahead_control *ractl,
{
struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
struct file_ra_state *ra = ractl->ra;
- unsigned long max_pages = ra->ra_pages;
unsigned long add_pages;
pgoff_t index = readahead_index(ractl);
+ unsigned long max_pages = ra_index_in_need_range(ra, index) ?
+ bdi->io_pages : ra->ra_pages;
pgoff_t expected, prev_index;
unsigned int order = folio ? folio_order(folio) : 0;
--
2.41.0
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