netdev - [net-next 2/3] eventpoll: Add per-epoll busy poll packet budget

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Message-Id: <20240124025359.11419-3-jdamato@fastly.com>
Date: Wed, 24 Jan 2024 02:53:58 +0000
From: Joe Damato <jdamato@...tly.com>
To: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: chuck.lever@...cle.com,
	jlayton@...nel.org,
	linux-api@...r.kernel.org,
	brauner@...nel.org,
	edumazet@...gle.com,
	davem@...emloft.net,
	alexander.duyck@...il.com,
	sridhar.samudrala@...el.com,
	kuba@...nel.org,
	Joe Damato <jdamato@...tly.com>
Subject: [net-next 2/3] eventpoll: Add per-epoll busy poll packet budget

When using epoll-based busy poll, the packet budget is hardcoded to
BUSY_POLL_BUDGET (8).

Add support for a per-epoll context busy poll packet budget. If not
specified, the default value (BUSY_POLL_BUDGET) is used.

Signed-off-by: Joe Damato <jdamato@...tly.com>
---
 fs/eventpoll.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 4503fec01278..40bd97477b91 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -229,6 +229,8 @@ struct eventpoll {
 	unsigned int napi_id;
 	/* busy poll timeout */
 	u64 busy_poll_usecs;
+	/* busy poll packet budget */
+	u16 busy_poll_budget;
 #endif
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -437,10 +439,14 @@ static bool ep_busy_loop_end(void *p, unsigned long start_time)
 static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
 {
 	unsigned int napi_id = READ_ONCE(ep->napi_id);
+	u16 budget = READ_ONCE(ep->busy_poll_budget);
+
+	if (!budget)
+		budget = BUSY_POLL_BUDGET;
 
 	if ((napi_id >= MIN_NAPI_ID) && ep_busy_loop_on(ep)) {
 		napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false,
-			       BUSY_POLL_BUDGET);
+			       budget);
 		if (ep_events_available(ep))
 			return true;
 		/*
@@ -2098,6 +2104,7 @@ static int do_epoll_create(int flags)
 	}
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	ep->busy_poll_usecs = 0;
+	ep->busy_poll_budget = 0;
 #endif
 	ep->file = file;
 	fd_install(fd, file);
-- 
2.25.1