On 4/6/22 21:33, Pavel Begunkov wrote:
io_uring deals with file reference loops by registering all fixed files
in the SCM/GC infrastrucure. However, only a small subset of all file
types can keep long-term references to other files and those that don't
are not interesting for the garbage collector as they can't be in a
reference loop. They neither can be directly recycled by GC nor affect
loop searching.
Let's skip io_uring SCM accounting for loop-less files, i.e. all but
af_unix sockets, quite imroving fixed file updates performance and
greatly helpnig with memory footprint.
Just to throw some numbers, simple loop with fixed file updates
in batches of 32 showed 2-3x performance improvement
(~400K-500K updates/s -> ~1.2M).
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 51 ++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 38 insertions(+), 13 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b4c85d85f88d..be178694e8db 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1211,6 +1211,18 @@ struct sock *io_uring_get_socket(struct file *file)
}
EXPORT_SYMBOL(io_uring_get_socket);
+#if defined(CONFIG_UNIX)
+static inline bool io_file_need_scm(struct file *filp)
+{
+ return !!unix_get_socket(filp);
+}
+#else
+static inline bool io_file_need_scm(struct file *filp)
+{
+ return 0;
+}
+#endif
+
static inline void io_tw_lock(struct io_ring_ctx *ctx, bool *locked)
{
if (!*locked) {
@@ -8424,6 +8436,17 @@ static void io_free_file_tables(struct io_file_table *table)
static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
+ int i;
+
+ for (i = 0; i < ctx->nr_user_files; i++) {
+ struct file *file = io_file_from_index(ctx, i);
+
+ if (!file || io_file_need_scm(file))
+ continue;
+ io_fixed_file_slot(&ctx->file_table, i)->file_ptr = 0;
+ fput(file);
+ }
+
#if defined(CONFIG_UNIX)
if (ctx->ring_sock) {
struct sock *sock = ctx->ring_sock->sk;
@@ -8432,16 +8455,6 @@ static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
kfree_skb(skb);
}
-#else
- int i;
-
- for (i = 0; i < ctx->nr_user_files; i++) {
- struct file *file;
-
- file = io_file_from_index(ctx, i);
- if (file)
- fput(file);
- }
#endif
io_free_file_tables(&ctx->file_table);
io_rsrc_data_free(ctx->file_data);
@@ -8590,7 +8603,9 @@ static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
/*
* Ensure the UNIX gc is aware of our file set, so we are certain that
* the io_uring can be safely unregistered on process exit, even if we have
- * loops in the file referencing.
+ * loops in the file referencing. We account only files that can hold other
+ * files because otherwise they can't form a loop and so are not interesting
+ * for GC.
*/
static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
{
@@ -8616,8 +8631,9 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
for (i = 0; i < nr; i++) {
struct file *file = io_file_from_index(ctx, i + offset);
- if (!file)
+ if (!file || !io_file_need_scm(file))
continue;
+
fpl->fp[nr_files] = get_file(file);
unix_inflight(fpl->user, fpl->fp[nr_files]);
nr_files++;
@@ -8634,7 +8650,7 @@ static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
for (i = 0; i < nr; i++) {
struct file *file = io_file_from_index(ctx, i + offset);
- if (file)
+ if (file && io_file_need_scm(file))
fput(file);
}
} else {
@@ -8676,6 +8692,7 @@ static int io_sqe_files_scm(struct io_ring_ctx *ctx)
if (file)
fput(file);
+ io_fixed_file_slot(&ctx->file_table, total)->file_ptr = 0;
total++;
}
@@ -8697,6 +8714,11 @@ static void io_rsrc_file_put(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc)
struct sk_buff *skb;
int i;
+ if (!io_file_need_scm(file)) {
+ fput(file);
+ return;
+ }
+
__skb_queue_head_init(&list);
/*
@@ -8889,6 +8911,9 @@ static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
struct sk_buff_head *head = &sock->sk_receive_queue;
struct sk_buff *skb;
+ if (!io_file_need_scm(file))
+ return 0;
+
/*
* See if we can merge this file into an existing skb SCM_RIGHTS
* file set. If there's no room, fall back to allocating a new skb
--
Pavel Begunkov
