From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit d9f21b3613337b55cc9d4a6ead484dca68475143 ]
If more than 16000 inflight AF_UNIX sockets exist and the garbage collector is not running, unix_(dgram|stream)_sendmsg() call unix_gc(). Also, they wait for unix_gc() to complete.
In unix_gc(), all inflight AF_UNIX sockets are traversed at least once, and more if they are the GC candidate. Thus, sendmsg() significantly slows down with too many inflight AF_UNIX sockets.
However, if a process sends data with no AF_UNIX FD, the sendmsg() call does not need to wait for GC. After this change, only the process that meets the condition below will be blocked under such a situation.
1) cmsg contains AF_UNIX socket 2) more than 32 AF_UNIX sent by the same user are still inflight
Note that even a sendmsg() call that does not meet the condition but has AF_UNIX FD will be blocked later in unix_scm_to_skb() by the spinlock, but we allow that as a bonus for sane users.
The results below are the time spent in unix_dgram_sendmsg() sending 1 byte of data with no FD 4096 times on a host where 32K inflight AF_UNIX sockets exist.
Without series: the sane sendmsg() needs to wait gc unreasonably.
$ sudo /usr/share/bcc/tools/funclatency -p 11165 unix_dgram_sendmsg Tracing 1 functions for "unix_dgram_sendmsg"... Hit Ctrl-C to end. ^C nsecs : count distribution [...] 524288 -> 1048575 : 0 | | 1048576 -> 2097151 : 3881 |****************************************| 2097152 -> 4194303 : 214 |** | 4194304 -> 8388607 : 1 | |
avg = 1825567 nsecs, total: 7477526027 nsecs, count: 4096
With series: the sane sendmsg() can finish much faster.
$ sudo /usr/share/bcc/tools/funclatency -p 8702 unix_dgram_sendmsg Tracing 1 functions for "unix_dgram_sendmsg"... Hit Ctrl-C to end. ^C nsecs : count distribution [...] 128 -> 255 : 0 | | 256 -> 511 : 4092 |****************************************| 512 -> 1023 : 2 | | 1024 -> 2047 : 0 | | 2048 -> 4095 : 0 | | 4096 -> 8191 : 1 | | 8192 -> 16383 : 1 | |
avg = 410 nsecs, total: 1680510 nsecs, count: 4096
Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Link: https://lore.kernel.org/r/20240123170856.41348-6-kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org (cherry picked from commit d9f21b3613337b55cc9d4a6ead484dca68475143) Signed-off-by: Lee Jones lee@kernel.org --- include/net/af_unix.h | 12 ++++++++++-- include/net/scm.h | 1 + net/core/scm.c | 5 +++++ net/unix/af_unix.c | 6 ++++-- net/unix/garbage.c | 10 +++++++++- 5 files changed, 29 insertions(+), 5 deletions(-)
diff --git a/include/net/af_unix.h b/include/net/af_unix.h index 7a00d7ed527b6..865e2f7bd67cf 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -8,13 +8,21 @@ #include <linux/refcount.h> #include <net/sock.h>
+#if IS_ENABLED(CONFIG_UNIX) +struct unix_sock *unix_get_socket(struct file *filp); +#else +static inline struct unix_sock *unix_get_socket(struct file *filp) +{ + return NULL; +} +#endif + void unix_inflight(struct user_struct *user, struct file *fp); void unix_notinflight(struct user_struct *user, struct file *fp); void unix_destruct_scm(struct sk_buff *skb); void io_uring_destruct_scm(struct sk_buff *skb); void unix_gc(void); -void wait_for_unix_gc(void); -struct unix_sock *unix_get_socket(struct file *filp); +void wait_for_unix_gc(struct scm_fp_list *fpl); struct sock *unix_peer_get(struct sock *sk);
#define UNIX_HASH_MOD (256 - 1) diff --git a/include/net/scm.h b/include/net/scm.h index e8c76b4be2fe7..1ff6a28550644 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -24,6 +24,7 @@ struct scm_creds {
struct scm_fp_list { short count; + short count_unix; short max; struct user_struct *user; struct file *fp[SCM_MAX_FD]; diff --git a/net/core/scm.c b/net/core/scm.c index 737917c7ac627..574607b1c2d96 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -36,6 +36,7 @@ #include <net/compat.h> #include <net/scm.h> #include <net/cls_cgroup.h> +#include <net/af_unix.h>
/* @@ -85,6 +86,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) return -ENOMEM; *fplp = fpl; fpl->count = 0; + fpl->count_unix = 0; fpl->max = SCM_MAX_FD; fpl->user = NULL; } @@ -109,6 +111,9 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) fput(file); return -EINVAL; } + if (unix_get_socket(file)) + fpl->count_unix++; + *fpp++ = file; fpl->count++; } diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index ab23c8d72122b..bb92b1ed94aaf 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1885,11 +1885,12 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg, long timeo; int err;
- wait_for_unix_gc(); err = scm_send(sock, msg, &scm, false); if (err < 0) return err;
+ wait_for_unix_gc(scm.fp); + err = -EOPNOTSUPP; if (msg->msg_flags&MSG_OOB) goto out; @@ -2157,11 +2158,12 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg, bool fds_sent = false; int data_len;
- wait_for_unix_gc(); err = scm_send(sock, msg, &scm, false); if (err < 0) return err;
+ wait_for_unix_gc(scm.fp); + err = -EOPNOTSUPP; if (msg->msg_flags & MSG_OOB) { #if IS_ENABLED(CONFIG_AF_UNIX_OOB) diff --git a/net/unix/garbage.c b/net/unix/garbage.c index a2a8543613a52..96cc6b7674333 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -335,8 +335,9 @@ void unix_gc(void) }
#define UNIX_INFLIGHT_TRIGGER_GC 16000 +#define UNIX_INFLIGHT_SANE_USER (SCM_MAX_FD * 8)
-void wait_for_unix_gc(void) +void wait_for_unix_gc(struct scm_fp_list *fpl) { /* If number of inflight sockets is insane, * force a garbage collect right now. @@ -348,6 +349,13 @@ void wait_for_unix_gc(void) !READ_ONCE(gc_in_progress)) unix_gc();
+ /* Penalise users who want to send AF_UNIX sockets + * but whose sockets have not been received yet. + */ + if (!fpl || !fpl->count_unix || + READ_ONCE(fpl->user->unix_inflight) < UNIX_INFLIGHT_SANE_USER) + return; + if (READ_ONCE(gc_in_progress)) flush_work(&unix_gc_work); }