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Mon, 04 Nov 2024 13:56:57 -0800 (PST) Received: from localhost.localdomain ([2620:11a:c019:0:65e:3115:2f58:c5fd]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-211057062b8sm65860255ad.63.2024.11.04.13.56.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Nov 2024 13:56:57 -0800 (PST) From: Joe Damato To: netdev@vger.kernel.org Cc: corbet@lwn.net, hdanton@sina.com, bagasdotme@gmail.com, pabeni@redhat.com, namangulati@google.com, edumazet@google.com, amritha.nambiar@intel.com, sridhar.samudrala@intel.com, sdf@fomichev.me, peter@typeblog.net, m2shafiei@uwaterloo.ca, bjorn@rivosinc.com, hch@infradead.org, willy@infradead.org, willemdebruijn.kernel@gmail.com, skhawaja@google.com, kuba@kernel.org, Martin Karsten , Joe Damato , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and infrastructure)), linux-kernel@vger.kernel.org (open list) Subject: [PATCH net-next v6 5/7] eventpoll: Control irq suspension for prefer_busy_poll Date: Mon, 4 Nov 2024 21:55:29 +0000 Message-Id: <20241104215542.215919-6-jdamato@fastly.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20241104215542.215919-1-jdamato@fastly.com> References: <20241104215542.215919-1-jdamato@fastly.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Martin Karsten When events are reported to userland and prefer_busy_poll is set, irqs are temporarily suspended using napi_suspend_irqs. If no events are found and ep_poll would go to sleep, irq suspension is cancelled using napi_resume_irqs. Signed-off-by: Martin Karsten Co-developed-by: Joe Damato Signed-off-by: Joe Damato Tested-by: Joe Damato Tested-by: Martin Karsten Acked-by: Stanislav Fomichev Reviewed-by: Sridhar Samudrala --- v5: - Only call ep_suspend_napi_irqs when ep_send_events returns a positive value. IRQs are not suspended in error (e.g. EINTR) cases. This issue was pointed out by Hillf Danton. rfc -> v1: - move irq resume code from ep_free to a helper which either resumes IRQs or does nothing if !defined(CONFIG_NET_RX_BUSY_POLL). fs/eventpoll.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index f9e0d9307dad..83bcb559b89f 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -457,6 +457,8 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonb= lock) * it back in when we have moved a socket with a valid NAPI * ID onto the ready list. */ + if (prefer_busy_poll) + napi_resume_irqs(napi_id); ep->napi_id =3D 0; return false; } @@ -540,6 +542,22 @@ static long ep_eventpoll_bp_ioctl(struct file *file, u= nsigned int cmd, } } =20 +static void ep_suspend_napi_irqs(struct eventpoll *ep) +{ + unsigned int napi_id =3D READ_ONCE(ep->napi_id); + + if (napi_id >=3D MIN_NAPI_ID && READ_ONCE(ep->prefer_busy_poll)) + napi_suspend_irqs(napi_id); +} + +static void ep_resume_napi_irqs(struct eventpoll *ep) +{ + unsigned int napi_id =3D READ_ONCE(ep->napi_id); + + if (napi_id >=3D MIN_NAPI_ID && READ_ONCE(ep->prefer_busy_poll)) + napi_resume_irqs(napi_id); +} + #else =20 static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) @@ -557,6 +575,14 @@ static long ep_eventpoll_bp_ioctl(struct file *file, u= nsigned int cmd, return -EOPNOTSUPP; } =20 +static void ep_suspend_napi_irqs(struct eventpoll *ep) +{ +} + +static void ep_resume_napi_irqs(struct eventpoll *ep) +{ +} + #endif /* CONFIG_NET_RX_BUSY_POLL */ =20 /* @@ -788,6 +814,7 @@ static bool ep_refcount_dec_and_test(struct eventpoll *= ep) =20 static void ep_free(struct eventpoll *ep) { + ep_resume_napi_irqs(ep); mutex_destroy(&ep->mtx); free_uid(ep->user); wakeup_source_unregister(ep->ws); @@ -2005,8 +2032,11 @@ static int ep_poll(struct eventpoll *ep, struct epol= l_event __user *events, * trying again in search of more luck. */ res =3D ep_send_events(ep, events, maxevents); - if (res) + if (res) { + if (res > 0) + ep_suspend_napi_irqs(ep); return res; + } } =20 if (timed_out) --=20 2.25.1