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Message-ID: <20231219030102.27509-5-kuniyu@amazon.com> Date: Tue, 19 Dec 2023 12:01:02 +0900 From: Kuniyuki Iwashima <kuniyu@...zon.com> To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com> CC: Ivan Babrou <ivan@...udflare.com>, Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima <kuni1840@...il.com>, <netdev@...r.kernel.org> Subject: [PATCH v4 net-next 4/4] af_unix: Try to run GC async. 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@...zon.com> --- include/net/af_unix.h | 2 +- include/net/scm.h | 1 + net/core/scm.c | 5 +++++ net/unix/af_unix.c | 6 ++++-- net/unix/garbage.c | 10 +++++++++- 5 files changed, 20 insertions(+), 4 deletions(-) diff --git a/include/net/af_unix.h b/include/net/af_unix.h index 2c98ef95017b..189e71c93a03 100644 --- a/include/net/af_unix.h +++ b/include/net/af_unix.h @@ -13,7 +13,7 @@ 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); +void wait_for_unix_gc(struct scm_fp_list *fpl); struct unix_sock *unix_get_socket(struct file *filp); struct sock *unix_peer_get(struct sock *sk); diff --git a/include/net/scm.h b/include/net/scm.h index e8c76b4be2fe..1ff6a2855064 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 7dc47c17d863..6341e56daedb 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> /* @@ -111,6 +112,10 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) } *fpp++ = file; fpl->count++; +#if IS_ENABLED(CONFIG_UNIX) + if (unix_get_socket(file)) + fpl->count_unix++; +#endif } if (!fpl->user) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 1e9378036dcc..1720419d93d6 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1923,11 +1923,12 @@ 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; @@ -2199,11 +2200,12 @@ 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 0dba36b0bb95..bf13357cc713 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -185,8 +185,9 @@ static void inc_inflight_move_tail(struct unix_sock *u) static bool gc_in_progress; #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. @@ -200,6 +201,13 @@ void wait_for_unix_gc(void) queue_work(system_unbound_wq, &unix_gc_work); } + /* 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); } -- 2.30.2
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