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-rw-r--r--fs/eventpoll.c93
1 files changed, 93 insertions, 0 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 341251421ced..5420767c9b68 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -42,6 +42,7 @@
#include <linux/seq_file.h>
#include <linux/compat.h>
#include <linux/rculist.h>
+#include <net/busy_poll.h>
/*
* LOCKING:
@@ -224,6 +225,11 @@ struct eventpoll {
/* used to optimize loop detection check */
int visited;
struct list_head visited_list_link;
+
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ /* used to track busy poll napi_id */
+ unsigned int napi_id;
+#endif
};
/* Wait structure used by the poll hooks */
@@ -384,6 +390,77 @@ static inline int ep_events_available(struct eventpoll *ep)
return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
}
+#ifdef CONFIG_NET_RX_BUSY_POLL
+static bool ep_busy_loop_end(void *p, unsigned long start_time)
+{
+ struct eventpoll *ep = p;
+
+ return ep_events_available(ep) || busy_loop_timeout(start_time);
+}
+#endif /* CONFIG_NET_RX_BUSY_POLL */
+
+/*
+ * Busy poll if globally on and supporting sockets found && no events,
+ * busy loop will return if need_resched or ep_events_available.
+ *
+ * we must do our busy polling with irqs enabled
+ */
+static void ep_busy_loop(struct eventpoll *ep, int nonblock)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ unsigned int napi_id = READ_ONCE(ep->napi_id);
+
+ if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on())
+ napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep);
+#endif
+}
+
+static inline void ep_reset_busy_poll_napi_id(struct eventpoll *ep)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ if (ep->napi_id)
+ ep->napi_id = 0;
+#endif
+}
+
+/*
+ * Set epoll busy poll NAPI ID from sk.
+ */
+static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ struct eventpoll *ep;
+ unsigned int napi_id;
+ struct socket *sock;
+ struct sock *sk;
+ int err;
+
+ if (!net_busy_loop_on())
+ return;
+
+ sock = sock_from_file(epi->ffd.file, &err);
+ if (!sock)
+ return;
+
+ sk = sock->sk;
+ if (!sk)
+ return;
+
+ napi_id = READ_ONCE(sk->sk_napi_id);
+ ep = epi->ep;
+
+ /* Non-NAPI IDs can be rejected
+ * or
+ * Nothing to do if we already have this ID
+ */
+ if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id)
+ return;
+
+ /* record NAPI ID for use in next busy poll */
+ ep->napi_id = napi_id;
+#endif
+}
+
/**
* ep_call_nested - Perform a bound (possibly) nested call, by checking
* that the recursion limit is not exceeded, and that
@@ -1022,6 +1099,8 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
spin_lock_irqsave(&ep->lock, flags);
+ ep_set_busy_poll_napi_id(epi);
+
/*
* If the event mask does not contain any poll(2) event, we consider the
* descriptor to be disabled. This condition is likely the effect of the
@@ -1363,6 +1442,9 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
/* We have to drop the new item inside our item list to keep track of it */
spin_lock_irqsave(&ep->lock, flags);
+ /* record NAPI ID of new item if present */
+ ep_set_busy_poll_napi_id(epi);
+
/* If the file is already "ready" we drop it inside the ready list */
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
@@ -1637,10 +1719,21 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
}
fetch_events:
+
+ if (!ep_events_available(ep))
+ ep_busy_loop(ep, timed_out);
+
spin_lock_irqsave(&ep->lock, flags);
if (!ep_events_available(ep)) {
/*
+ * Busy poll timed out. Drop NAPI ID for now, we can add
+ * it back in when we have moved a socket with a valid NAPI
+ * ID onto the ready list.
+ */
+ ep_reset_busy_poll_napi_id(ep);
+
+ /*
* We don't have any available event to return to the caller.
* We need to sleep here, and we will be wake up by
* ep_poll_callback() when events will become available.