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-rw-r--r--Documentation/sysctl/net.txt18
-rw-r--r--fs/select.c34
-rw-r--r--include/net/ll_poll.h35
-rw-r--r--include/uapi/asm-generic/poll.h2
-rw-r--r--net/core/sock.c2
-rw-r--r--net/core/sysctl_net_core.c8
-rw-r--r--net/socket.c14
7 files changed, 91 insertions, 22 deletions
diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt
index 5369879eafe2..e658bbfb641f 100644
--- a/Documentation/sysctl/net.txt
+++ b/Documentation/sysctl/net.txt
@@ -50,13 +50,27 @@ The maximum number of packets that kernel can handle on a NAPI interrupt,
it's a Per-CPU variable.
Default: 64
-low_latency_poll
+low_latency_read
----------------
-Low latency busy poll timeout. (needs CONFIG_NET_LL_RX_POLL)
+Low latency busy poll timeout for socket reads. (needs CONFIG_NET_LL_RX_POLL)
Approximate time in us to spin waiting for packets on the device queue.
+This sets the default value of the SO_LL socket option.
+Can be set or overridden per socket by setting socket option SO_LL.
Recommended value is 50. May increase power usage.
Default: 0 (off)
+low_latency_poll
+----------------
+Low latency busy poll timeout for poll and select. (needs CONFIG_NET_LL_RX_POLL)
+Approximate time in us to spin waiting for packets on the device queue.
+Recommended value depends on the number of sockets you poll on.
+For several sockets 50, for several hundreds 100.
+For more than that you probably want to use epoll.
+Note that only sockets with SO_LL set will be busy polled, so you want to either
+selectively set SO_LL on those sockets or set sysctl.net.low_latency_read globally.
+May increase power usage.
+Default: 0 (off)
+
rmem_default
------------
diff --git a/fs/select.c b/fs/select.c
index 8c1c96c27062..79b876eb91da 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -27,6 +27,7 @@
#include <linux/rcupdate.h>
#include <linux/hrtimer.h>
#include <linux/sched/rt.h>
+#include <net/ll_poll.h>
#include <asm/uaccess.h>
@@ -384,9 +385,10 @@ get_max:
#define POLLEX_SET (POLLPRI)
static inline void wait_key_set(poll_table *wait, unsigned long in,
- unsigned long out, unsigned long bit)
+ unsigned long out, unsigned long bit,
+ unsigned int ll_flag)
{
- wait->_key = POLLEX_SET;
+ wait->_key = POLLEX_SET | ll_flag;
if (in & bit)
wait->_key |= POLLIN_SET;
if (out & bit)
@@ -400,6 +402,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
poll_table *wait;
int retval, i, timed_out = 0;
unsigned long slack = 0;
+ unsigned int ll_flag = POLL_LL;
+ u64 ll_time = ll_end_time();
rcu_read_lock();
retval = max_select_fd(n, fds);
@@ -422,6 +426,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
retval = 0;
for (;;) {
unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
+ bool can_ll = false;
inp = fds->in; outp = fds->out; exp = fds->ex;
rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
@@ -449,7 +454,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
f_op = f.file->f_op;
mask = DEFAULT_POLLMASK;
if (f_op && f_op->poll) {
- wait_key_set(wait, in, out, bit);
+ wait_key_set(wait, in, out,
+ bit, ll_flag);
mask = (*f_op->poll)(f.file, wait);
}
fdput(f);
@@ -468,6 +474,11 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
retval++;
wait->_qproc = NULL;
}
+ if (mask & POLL_LL)
+ can_ll = true;
+ /* got something, stop busy polling */
+ if (retval)
+ ll_flag = 0;
}
}
if (res_in)
@@ -486,6 +497,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
break;
}
+ if (can_ll && can_poll_ll(ll_time))
+ continue;
+
/*
* If this is the first loop and we have a timeout
* given, then we convert to ktime_t and set the to
@@ -717,7 +731,8 @@ struct poll_list {
* pwait poll_table will be used by the fd-provided poll handler for waiting,
* if pwait->_qproc is non-NULL.
*/
-static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
+static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
+ bool *can_ll, unsigned int ll_flag)
{
unsigned int mask;
int fd;
@@ -731,7 +746,10 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
mask = DEFAULT_POLLMASK;
if (f.file->f_op && f.file->f_op->poll) {
pwait->_key = pollfd->events|POLLERR|POLLHUP;
+ pwait->_key |= ll_flag;
mask = f.file->f_op->poll(f.file, pwait);
+ if (mask & POLL_LL)
+ *can_ll = true;
}
/* Mask out unneeded events. */
mask &= pollfd->events | POLLERR | POLLHUP;
@@ -750,6 +768,8 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
ktime_t expire, *to = NULL;
int timed_out = 0, count = 0;
unsigned long slack = 0;
+ unsigned int ll_flag = POLL_LL;
+ u64 ll_time = ll_end_time();
/* Optimise the no-wait case */
if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
@@ -762,6 +782,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
for (;;) {
struct poll_list *walk;
+ bool can_ll = false;
for (walk = list; walk != NULL; walk = walk->next) {
struct pollfd * pfd, * pfd_end;
@@ -776,9 +797,10 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
* this. They'll get immediately deregistered
* when we break out and return.
*/
- if (do_pollfd(pfd, pt)) {
+ if (do_pollfd(pfd, pt, &can_ll, ll_flag)) {
count++;
pt->_qproc = NULL;
+ ll_flag = 0;
}
}
}
@@ -795,6 +817,8 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
if (count || timed_out)
break;
+ if (can_ll && can_poll_ll(ll_time))
+ continue;
/*
* If this is the first loop and we have a timeout
* given, then we convert to ktime_t and set the to
diff --git a/include/net/ll_poll.h b/include/net/ll_poll.h
index fcc7c365cee5..5bf2b3a6129e 100644
--- a/include/net/ll_poll.h
+++ b/include/net/ll_poll.h
@@ -30,6 +30,7 @@
#ifdef CONFIG_NET_LL_RX_POLL
struct napi_struct;
+extern unsigned int sysctl_net_ll_read __read_mostly;
extern unsigned int sysctl_net_ll_poll __read_mostly;
/* return values from ndo_ll_poll */
@@ -38,17 +39,18 @@ extern unsigned int sysctl_net_ll_poll __read_mostly;
/* we can use sched_clock() because we don't care much about precision
* we only care that the average is bounded
+ * we don't mind a ~2.5% imprecision so <<10 instead of *1000
+ * sk->sk_ll_usec is a u_int so this can't overflow
*/
-static inline u64 ll_end_time(struct sock *sk)
+static inline u64 ll_sk_end_time(struct sock *sk)
{
- u64 end_time = ACCESS_ONCE(sk->sk_ll_usec);
-
- /* we don't mind a ~2.5% imprecision
- * sk->sk_ll_usec is a u_int so this can't overflow
- */
- end_time = (end_time << 10) + sched_clock();
+ return ((u64)ACCESS_ONCE(sk->sk_ll_usec) << 10) + sched_clock();
+}
- return end_time;
+/* in poll/select we use the global sysctl_net_ll_poll value */
+static inline u64 ll_end_time(void)
+{
+ return ((u64)ACCESS_ONCE(sysctl_net_ll_poll) << 10) + sched_clock();
}
static inline bool sk_valid_ll(struct sock *sk)
@@ -62,10 +64,13 @@ static inline bool can_poll_ll(u64 end_time)
return !time_after64(sched_clock(), end_time);
}
+/* when used in sock_poll() nonblock is known at compile time to be true
+ * so the loop and end_time will be optimized out
+ */
static inline bool sk_poll_ll(struct sock *sk, int nonblock)
{
+ u64 end_time = nonblock ? 0 : ll_sk_end_time(sk);
const struct net_device_ops *ops;
- u64 end_time = ll_end_time(sk);
struct napi_struct *napi;
int rc = false;
@@ -84,7 +89,6 @@ static inline bool sk_poll_ll(struct sock *sk, int nonblock)
goto out;
do {
-
rc = ops->ndo_ll_poll(napi);
if (rc == LL_FLUSH_FAILED)
@@ -95,8 +99,8 @@ static inline bool sk_poll_ll(struct sock *sk, int nonblock)
NET_ADD_STATS_BH(sock_net(sk),
LINUX_MIB_LOWLATENCYRXPACKETS, rc);
- } while (skb_queue_empty(&sk->sk_receive_queue)
- && can_poll_ll(end_time) && !nonblock);
+ } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
+ can_poll_ll(end_time));
rc = !skb_queue_empty(&sk->sk_receive_queue);
out:
@@ -118,7 +122,12 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
#else /* CONFIG_NET_LL_RX_POLL */
-static inline u64 ll_end_time(struct sock *sk)
+static inline u64 sk_ll_end_time(struct sock *sk)
+{
+ return 0;
+}
+
+static inline u64 ll_end_time(void)
{
return 0;
}
diff --git a/include/uapi/asm-generic/poll.h b/include/uapi/asm-generic/poll.h
index 9ce7f44aebd2..4aee586979ca 100644
--- a/include/uapi/asm-generic/poll.h
+++ b/include/uapi/asm-generic/poll.h
@@ -30,6 +30,8 @@
#define POLLFREE 0x4000 /* currently only for epoll */
+#define POLL_LL 0x8000
+
struct pollfd {
int fd;
short events;
diff --git a/net/core/sock.c b/net/core/sock.c
index 1e744b12fda3..b6c619f4d47b 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2307,7 +2307,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
#ifdef CONFIG_NET_LL_RX_POLL
sk->sk_napi_id = 0;
- sk->sk_ll_usec = sysctl_net_ll_poll;
+ sk->sk_ll_usec = sysctl_net_ll_read;
#endif
/*
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 62702c2053de..afc677eadd93 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -306,6 +306,14 @@ static struct ctl_table net_core_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "low_latency_read",
+ .data = &sysctl_net_ll_read,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
+#
#endif
#endif /* CONFIG_NET */
{
diff --git a/net/socket.c b/net/socket.c
index 3eec3f76b49c..4da14cbd49b6 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -107,6 +107,7 @@
#include <net/ll_poll.h>
#ifdef CONFIG_NET_LL_RX_POLL
+unsigned int sysctl_net_ll_read __read_mostly;
unsigned int sysctl_net_ll_poll __read_mostly;
#endif
@@ -1147,13 +1148,24 @@ EXPORT_SYMBOL(sock_create_lite);
/* No kernel lock held - perfect */
static unsigned int sock_poll(struct file *file, poll_table *wait)
{
+ unsigned int ll_flag = 0;
struct socket *sock;
/*
* We can't return errors to poll, so it's either yes or no.
*/
sock = file->private_data;
- return sock->ops->poll(file, sock, wait);
+
+ if (sk_valid_ll(sock->sk)) {
+ /* this socket can poll_ll so tell the system call */
+ ll_flag = POLL_LL;
+
+ /* once, only if requested by syscall */
+ if (wait && (wait->_key & POLL_LL))
+ sk_poll_ll(sock->sk, 1);
+ }
+
+ return ll_flag | sock->ops->poll(file, sock, wait);
}
static int sock_mmap(struct file *file, struct vm_area_struct *vma)
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-14 08:49:12 +0100