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authorEliezer Tamir <eliezer.tamir@linux.intel.com>2013-06-24 10:28:03 +0300
committerDavid S. Miller <davem@davemloft.net>2013-06-25 16:35:52 -0700
commit2d48d67fa8cd129ea85ea02d91b4a793286866f8 (patch)
treebe47e2406605760d949b08d29d988d46c4a20799 /fs/select.c
parente4f2379db6c6823c5d4a4c2c912df00c65de51d7 (diff)
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net: poll/select low latency socket support
select/poll busy-poll support. Split sysctl value into two separate ones, one for read and one for poll. updated Documentation/sysctl/net.txt Add a new poll flag POLL_LL. When this flag is set, sock_poll will call sk_poll_ll if possible. sock_poll sets this flag in its return value to indicate to select/poll when a socket that can busy poll is found. When poll/select have nothing to report, call the low-level sock_poll again until we are out of time or we find something. Once the system call finds something, it stops setting POLL_LL, so it can return the result to the user ASAP. Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'fs/select.c')
-rw-r--r--fs/select.c34
1 files changed, 29 insertions, 5 deletions
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