net: rename low latency sockets functions to busy poll
Rename functions in include/net/ll_poll.h to busy wait. Clarify documentation about expected power use increase. Rename POLL_LL to POLL_BUSY_LOOP. Add need_resched() testing to poll/select busy loops. Note, that in select and poll can_busy_poll is dynamic and is updated continuously to reflect the existence of supported sockets with valid queue information. Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eliezer Tamir
David S. Miller
Родитель
c7e8e8a8f7
Коммит
cbf55001b2
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@ -53,22 +53,24 @@ Default: 64
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low_latency_read
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----------------
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Low latency busy poll timeout for socket reads. (needs CONFIG_NET_LL_RX_POLL)
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Approximate time in us to spin waiting for packets on the device queue.
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Approximate time in us to busy loop waiting for packets on the device queue.
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This sets the default value of the SO_LL socket option.
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Can be set or overridden per socket by setting socket option SO_LL.
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Recommended value is 50. May increase power usage.
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Can be set or overridden per socket by setting socket option SO_LL, which is
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the preferred method of enabling.
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If you need to enable the feature globally via sysctl, a value of 50 is recommended.
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Will increase power usage.
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Default: 0 (off)
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low_latency_poll
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----------------
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Low latency busy poll timeout for poll and select. (needs CONFIG_NET_LL_RX_POLL)
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Approximate time in us to spin waiting for packets on the device queue.
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Approximate time in us to busy loop waiting for events.
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Recommended value depends on the number of sockets you poll on.
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For several sockets 50, for several hundreds 100.
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For more than that you probably want to use epoll.
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Note that only sockets with SO_LL set will be busy polled, so you want to either
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selectively set SO_LL on those sockets or set sysctl.net.low_latency_read globally.
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May increase power usage.
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Will increase power usage.
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Default: 0 (off)
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rmem_default
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60
fs/select.c
60
fs/select.c
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@ -402,9 +402,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
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poll_table *wait;
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int retval, i, timed_out = 0;
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unsigned long slack = 0;
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unsigned int ll_flag = ll_get_flag();
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u64 ll_start = ll_start_time(ll_flag);
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u64 ll_time = ll_run_time();
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unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
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u64 busy_start = busy_loop_start_time(busy_flag);
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u64 busy_end = busy_loop_end_time();
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rcu_read_lock();
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retval = max_select_fd(n, fds);
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@ -427,7 +427,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
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retval = 0;
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for (;;) {
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unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
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bool can_ll = false;
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bool can_busy_loop = false;
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inp = fds->in; outp = fds->out; exp = fds->ex;
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rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
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@ -456,7 +456,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
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mask = DEFAULT_POLLMASK;
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if (f_op && f_op->poll) {
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wait_key_set(wait, in, out,
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bit, ll_flag);
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bit, busy_flag);
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mask = (*f_op->poll)(f.file, wait);
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}
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fdput(f);
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@ -475,11 +475,18 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
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retval++;
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wait->_qproc = NULL;
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}
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if (mask & POLL_LL)
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can_ll = true;
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/* got something, stop busy polling */
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if (retval)
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ll_flag = 0;
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if (retval) {
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can_busy_loop = false;
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busy_flag = 0;
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/*
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* only remember a returned
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* POLL_BUSY_LOOP if we asked for it
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*/
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} else if (busy_flag & mask)
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can_busy_loop = true;
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}
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}
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if (res_in)
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@ -498,8 +505,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
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break;
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}
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/* only if on, have sockets with POLL_LL and not out of time */
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if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
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/* only if found POLL_BUSY_LOOP sockets && not out of time */
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if (!need_resched() && can_busy_loop &&
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busy_loop_range(busy_start, busy_end))
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continue;
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/*
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@ -734,7 +742,8 @@ struct poll_list {
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* if pwait->_qproc is non-NULL.
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*/
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static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
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bool *can_ll, unsigned int ll_flag)
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bool *can_busy_poll,
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unsigned int busy_flag)
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{
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unsigned int mask;
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int fd;
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@ -748,10 +757,10 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
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mask = DEFAULT_POLLMASK;
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if (f.file->f_op && f.file->f_op->poll) {
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pwait->_key = pollfd->events|POLLERR|POLLHUP;
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pwait->_key |= ll_flag;
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pwait->_key |= busy_flag;
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mask = f.file->f_op->poll(f.file, pwait);
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if (mask & POLL_LL)
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*can_ll = true;
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if (mask & busy_flag)
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*can_busy_poll = true;
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}
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/* Mask out unneeded events. */
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mask &= pollfd->events | POLLERR | POLLHUP;
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@ -770,9 +779,10 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
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ktime_t expire, *to = NULL;
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int timed_out = 0, count = 0;
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unsigned long slack = 0;
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unsigned int ll_flag = ll_get_flag();
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u64 ll_start = ll_start_time(ll_flag);
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u64 ll_time = ll_run_time();
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unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
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u64 busy_start = busy_loop_start_time(busy_flag);
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u64 busy_end = busy_loop_end_time();
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/* Optimise the no-wait case */
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if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
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@ -785,7 +795,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
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for (;;) {
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struct poll_list *walk;
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bool can_ll = false;
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bool can_busy_loop = false;
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for (walk = list; walk != NULL; walk = walk->next) {
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struct pollfd * pfd, * pfd_end;
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@ -800,10 +810,13 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
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* this. They'll get immediately deregistered
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* when we break out and return.
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*/
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if (do_pollfd(pfd, pt, &can_ll, ll_flag)) {
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if (do_pollfd(pfd, pt, &can_busy_loop,
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busy_flag)) {
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count++;
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pt->_qproc = NULL;
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ll_flag = 0;
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/* found something, stop busy polling */
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busy_flag = 0;
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can_busy_loop = false;
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}
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}
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}
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@ -820,8 +833,9 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
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if (count || timed_out)
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break;
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/* only if on, have sockets with POLL_LL and not out of time */
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if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
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/* only if found POLL_BUSY_LOOP sockets && not out of time */
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if (!need_resched() && can_busy_loop &&
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busy_loop_range(busy_start, busy_end))
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continue;
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/*
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@ -37,9 +37,9 @@ extern unsigned int sysctl_net_ll_poll __read_mostly;
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#define LL_FLUSH_FAILED -1
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#define LL_FLUSH_BUSY -2
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static inline unsigned int ll_get_flag(void)
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static inline bool net_busy_loop_on(void)
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{
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return sysctl_net_ll_poll ? POLL_LL : 0;
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return sysctl_net_ll_poll;
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}
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/* a wrapper to make debug_smp_processor_id() happy
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@ -47,7 +47,7 @@ static inline unsigned int ll_get_flag(void)
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* we only care that the average is bounded
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*/
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#ifdef CONFIG_DEBUG_PREEMPT
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static inline u64 ll_sched_clock(void)
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static inline u64 busy_loop_sched_clock(void)
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{
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u64 rc;
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@ -58,7 +58,7 @@ static inline u64 ll_sched_clock(void)
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return rc;
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}
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#else /* CONFIG_DEBUG_PREEMPT */
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static inline u64 ll_sched_clock(void)
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static inline u64 busy_loop_sched_clock(void)
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{
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return sched_clock();
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}
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@ -67,7 +67,7 @@ static inline u64 ll_sched_clock(void)
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/* we don't mind a ~2.5% imprecision so <<10 instead of *1000
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* sk->sk_ll_usec is a u_int so this can't overflow
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*/
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static inline u64 ll_sk_run_time(struct sock *sk)
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static inline u64 sk_busy_loop_end_time(struct sock *sk)
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{
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return (u64)ACCESS_ONCE(sk->sk_ll_usec) << 10;
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}
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@ -75,27 +75,29 @@ static inline u64 ll_sk_run_time(struct sock *sk)
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/* in poll/select we use the global sysctl_net_ll_poll value
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* only call sched_clock() if enabled
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*/
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static inline u64 ll_run_time(void)
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static inline u64 busy_loop_end_time(void)
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{
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return (u64)ACCESS_ONCE(sysctl_net_ll_poll) << 10;
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}
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/* if flag is not set we don't need to know the time */
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static inline u64 ll_start_time(unsigned int flag)
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/* if flag is not set we don't need to know the time
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* so we want to avoid a potentially expensive sched_clock()
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*/
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static inline u64 busy_loop_start_time(unsigned int flag)
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{
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return flag ? ll_sched_clock() : 0;
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return flag ? busy_loop_sched_clock() : 0;
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}
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static inline bool sk_valid_ll(struct sock *sk)
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static inline bool sk_can_busy_loop(struct sock *sk)
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{
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return sk->sk_ll_usec && sk->sk_napi_id &&
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!need_resched() && !signal_pending(current);
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}
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/* careful! time_in_range64 will evaluate now twice */
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static inline bool can_poll_ll(u64 start_time, u64 run_time)
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static inline bool busy_loop_range(u64 start_time, u64 run_time)
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{
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u64 now = ll_sched_clock();
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u64 now = busy_loop_sched_clock();
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return time_in_range64(now, start_time, start_time + run_time);
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}
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@ -103,10 +105,10 @@ static inline bool can_poll_ll(u64 start_time, u64 run_time)
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/* when used in sock_poll() nonblock is known at compile time to be true
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* so the loop and end_time will be optimized out
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*/
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static inline bool sk_poll_ll(struct sock *sk, int nonblock)
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static inline bool sk_busy_loop(struct sock *sk, int nonblock)
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{
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u64 start_time = ll_start_time(!nonblock);
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u64 run_time = ll_sk_run_time(sk);
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u64 start_time = busy_loop_start_time(!nonblock);
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u64 end_time = sk_busy_loop_end_time(sk);
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const struct net_device_ops *ops;
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struct napi_struct *napi;
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int rc = false;
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@ -137,7 +139,7 @@ static inline bool sk_poll_ll(struct sock *sk, int nonblock)
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LINUX_MIB_LOWLATENCYRXPACKETS, rc);
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} while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
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can_poll_ll(start_time, run_time));
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busy_loop_range(start_time, end_time));
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rc = !skb_queue_empty(&sk->sk_receive_queue);
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out:
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@ -158,27 +160,27 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
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}
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#else /* CONFIG_NET_LL_RX_POLL */
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static inline unsigned long ll_get_flag(void)
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static inline unsigned long net_busy_loop_on(void)
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{
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return 0;
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}
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static inline u64 ll_start_time(unsigned int flag)
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static inline u64 busy_loop_start_time(unsigned int flag)
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{
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return 0;
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}
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static inline u64 ll_run_time(void)
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static inline u64 busy_loop_end_time(void)
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{
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return 0;
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}
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static inline bool sk_valid_ll(struct sock *sk)
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static inline bool sk_can_busy_loop(struct sock *sk)
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{
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return false;
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}
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static inline bool sk_poll_ll(struct sock *sk, int nonblock)
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static inline bool sk_busy_poll(struct sock *sk, int nonblock)
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{
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return false;
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}
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@ -191,7 +193,7 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
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{
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}
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static inline bool can_poll_ll(u64 start_time, u64 run_time)
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static inline bool busy_loop_range(u64 start_time, u64 run_time)
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{
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return false;
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}
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@ -30,7 +30,7 @@
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#define POLLFREE 0x4000 /* currently only for epoll */
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#define POLL_LL 0x8000
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#define POLL_BUSY_LOOP 0x8000
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struct pollfd {
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int fd;
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@ -208,7 +208,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
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}
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spin_unlock_irqrestore(&queue->lock, cpu_flags);
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if (sk_valid_ll(sk) && sk_poll_ll(sk, flags & MSG_DONTWAIT))
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if (sk_can_busy_loop(sk) &&
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sk_busy_loop(sk, flags & MSG_DONTWAIT))
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continue;
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/* User doesn't want to wait */
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@ -1554,9 +1554,9 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
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struct sk_buff *skb;
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u32 urg_hole = 0;
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if (sk_valid_ll(sk) && skb_queue_empty(&sk->sk_receive_queue)
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&& (sk->sk_state == TCP_ESTABLISHED))
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sk_poll_ll(sk, nonblock);
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if (sk_can_busy_loop(sk) && skb_queue_empty(&sk->sk_receive_queue) &&
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(sk->sk_state == TCP_ESTABLISHED))
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sk_busy_loop(sk, nonblock);
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lock_sock(sk);
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12
net/socket.c
12
net/socket.c
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@ -1148,7 +1148,7 @@ EXPORT_SYMBOL(sock_create_lite);
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/* No kernel lock held - perfect */
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static unsigned int sock_poll(struct file *file, poll_table *wait)
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{
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unsigned int ll_flag = 0;
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unsigned int busy_flag = 0;
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struct socket *sock;
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/*
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@ -1156,16 +1156,16 @@ static unsigned int sock_poll(struct file *file, poll_table *wait)
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*/
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sock = file->private_data;
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if (sk_valid_ll(sock->sk)) {
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if (sk_can_busy_loop(sock->sk)) {
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/* this socket can poll_ll so tell the system call */
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ll_flag = POLL_LL;
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busy_flag = POLL_BUSY_LOOP;
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/* once, only if requested by syscall */
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if (wait && (wait->_key & POLL_LL))
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sk_poll_ll(sock->sk, 1);
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if (wait && (wait->_key & POLL_BUSY_LOOP))
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sk_busy_loop(sock->sk, 1);
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}
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return ll_flag | sock->ops->poll(file, sock, wait);
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return busy_flag | sock->ops->poll(file, sock, wait);
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}
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static int sock_mmap(struct file *file, struct vm_area_struct *vma)
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