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The per-epoll context usec timeout value is preferred, but the pre-existing system wide sysctl value is still supported if it specified. Note that this change uses an xor: either per epoll instance busy polling is enabled on the epoll instance or system wide epoll is enabled. Enabling both is disallowed. Signed-off-by: Joe Damato --- fs/eventpoll.c | 49 +++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 45 insertions(+), 4 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 3534d36a1474..ce75189d46df 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -227,6 +227,8 @@ struct eventpoll { #ifdef CONFIG_NET_RX_BUSY_POLL /* used to track busy poll napi_id */ unsigned int napi_id; + /* busy poll timeout */ + u64 busy_poll_usecs; #endif =20 #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -386,12 +388,44 @@ static inline int ep_events_available(struct eventpol= l *ep) READ_ONCE(ep->ovflist) !=3D EP_UNACTIVE_PTR; } =20 +/** + * busy_loop_ep_timeout - check if busy poll has timed out. The timeout va= lue + * from the epoll instance ep is preferred, but if it is not set fallback = to + * the system-wide global via busy_loop_timeout. + * + * @start_time: The start time used to compute the remaining time until ti= meout. + * @ep: Pointer to the eventpoll context. + * + * Return: true if the timeout has expired, false otherwise. + */ +static inline bool busy_loop_ep_timeout(unsigned long start_time, struct e= ventpoll *ep) +{ +#ifdef CONFIG_NET_RX_BUSY_POLL + unsigned long bp_usec =3D READ_ONCE(ep->busy_poll_usecs); + + if (bp_usec) { + unsigned long end_time =3D start_time + bp_usec; + unsigned long now =3D busy_loop_current_time(); + + return time_after(now, end_time); + } else { + return busy_loop_timeout(start_time); + } +#endif + return true; +} + #ifdef CONFIG_NET_RX_BUSY_POLL +static bool ep_busy_loop_on(struct eventpoll *ep) +{ + return !!ep->busy_poll_usecs || net_busy_loop_on(); +} + static bool ep_busy_loop_end(void *p, unsigned long start_time) { struct eventpoll *ep =3D p; =20 - return ep_events_available(ep) || busy_loop_timeout(start_time); + return ep_events_available(ep) || busy_loop_ep_timeout(start_time, ep); } =20 /* @@ -404,7 +438,7 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonb= lock) { unsigned int napi_id =3D READ_ONCE(ep->napi_id); =20 - if ((napi_id >=3D MIN_NAPI_ID) && net_busy_loop_on()) { + if ((napi_id >=3D MIN_NAPI_ID) && ep_busy_loop_on(ep)) { napi_busy_loop(napi_id, nonblock ? 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charset="utf-8" When using epoll-based busy poll, the packet budget is hardcoded to BUSY_POLL_BUDGET (8). Users may desire larger busy poll budgets, which can potentially increase throughput when busy polling under high network load. Other busy poll methods allow setting the busy poll budget via SO_BUSY_POLL_BUDGET, but epoll-based busy polling uses a hardcoded value. Fix this edge case by adding 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 --- fs/eventpoll.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index ce75189d46df..3985434df527 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 =20 #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -437,10 +439,14 @@ static bool ep_busy_loop_end(void *p, unsigned long s= tart_time) static bool ep_busy_loop(struct eventpoll *ep, int nonblock) { unsigned int napi_id =3D READ_ONCE(ep->napi_id); + u16 budget =3D READ_ONCE(ep->busy_poll_budget); + + if (!budget) + budget =3D BUSY_POLL_BUDGET; =20 if ((napi_id >=3D MIN_NAPI_ID) && ep_busy_loop_on(ep)) { napi_busy_loop(napi_id, nonblock ? 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Wed, 31 Jan 2024 10:09:46 -0800 (PST) Received: from localhost.localdomain ([2620:11a:c018:0:ea8:be91:8d1:f59b]) by smtp.gmail.com with ESMTPSA id v24-20020a634818000000b005cfbf96c733sm10876004pga.30.2024.01.31.10.09.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 10:09:46 -0800 (PST) From: Joe Damato To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: chuck.lever@oracle.com, jlayton@kernel.org, linux-api@vger.kernel.org, brauner@kernel.org, edumazet@google.com, davem@davemloft.net, alexander.duyck@gmail.com, sridhar.samudrala@intel.com, kuba@kernel.org, willemdebruijn.kernel@gmail.com, weiwan@google.com, David.Laight@ACULAB.COM, arnd@arndb.de, Joe Damato , Jonathan Corbet , Alexander Viro , Jan Kara , Greg Kroah-Hartman , Nathan Lynch , Michael Ellerman , Dominik Brodowski , Steve French , Julien Panis , Thomas Zimmermann , Jiri Slaby , Thomas Huth , Albert Ou , Andrew Waterman , Palmer Dabbelt , linux-doc@vger.kernel.org (open list:DOCUMENTATION), linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS and infrastructure)) Subject: [PATCH net-next v5 3/3] eventpoll: Add epoll ioctl for epoll_params Date: Wed, 31 Jan 2024 18:08:05 +0000 Message-Id: <20240131180811.23566-4-jdamato@fastly.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240131180811.23566-1-jdamato@fastly.com> References: <20240131180811.23566-1-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" Add an ioctl for getting and setting epoll_params. User programs can use this ioctl to get and set the busy poll usec time or packet budget params for a specific epoll context. Parameters are limited: - busy_poll_usecs is limited to <=3D u32_max - busy_poll_budget is limited to <=3D NAPI_POLL_WEIGHT by unprivileged users (!capable(CAP_NET_ADMIN)). - __pad must be 0 Signed-off-by: Joe Damato --- .../userspace-api/ioctl/ioctl-number.rst | 1 + fs/eventpoll.c | 68 +++++++++++++++++++ include/uapi/linux/eventpoll.h | 12 ++++ 3 files changed, 81 insertions(+) diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documenta= tion/userspace-api/ioctl/ioctl-number.rst index 457e16f06e04..b33918232f78 100644 --- a/Documentation/userspace-api/ioctl/ioctl-number.rst +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst @@ -309,6 +309,7 @@ Code Seq# Include File = Comments 0x89 0B-DF linux/sockios.h 0x89 E0-EF linux/sockios.h SIOCP= ROTOPRIVATE range 0x89 F0-FF linux/sockios.h SIOCD= EVPRIVATE range +0x8A 00-1F linux/eventpoll.h 0x8B all linux/wireless.h 0x8C 00-3F WiNRA= DiO driver diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 3985434df527..96efca6a9238 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -37,6 +37,7 @@ #include #include #include +#include #include =20 /* @@ -495,6 +496,45 @@ static inline void ep_set_busy_poll_napi_id(struct epi= tem *epi) ep->napi_id =3D napi_id; } =20 +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct eventpoll *ep; + struct epoll_params epoll_params; + void __user *uarg =3D (void __user *) arg; + + ep =3D file->private_data; + + switch (cmd) { + case EPIOCSPARAMS: + if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params))) + return -EFAULT; + + if (memchr_inv(epoll_params.__pad, 0, sizeof(epoll_params.__pad))) + return -EINVAL; + + if (epoll_params.busy_poll_usecs > U32_MAX) + return -EINVAL; + + if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT && + !capable(CAP_NET_ADMIN)) + return -EPERM; + + ep->busy_poll_usecs =3D epoll_params.busy_poll_usecs; + ep->busy_poll_budget =3D epoll_params.busy_poll_budget; + return 0; + case EPIOCGPARAMS: + memset(&epoll_params, 0, sizeof(epoll_params)); + epoll_params.busy_poll_usecs =3D ep->busy_poll_usecs; + epoll_params.busy_poll_budget =3D ep->busy_poll_budget; + if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params))) + return -EFAULT; + return 0; + default: + return -ENOIOCTLCMD; + } +} + #else =20 static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) @@ -510,6 +550,12 @@ static inline bool ep_busy_loop_on(struct eventpoll *e= p) { return false; } + +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_NET_RX_BUSY_POLL */ =20 /* @@ -869,6 +915,26 @@ static void ep_clear_and_put(struct eventpoll *ep) ep_free(ep); } =20 +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsign= ed long arg) +{ + int ret; + + if (!is_file_epoll(file)) + return -EINVAL; + + switch (cmd) { + case EPIOCSPARAMS: + case EPIOCGPARAMS: + ret =3D ep_eventpoll_bp_ioctl(file, cmd, arg); + break; + default: + ret =3D -EINVAL; + break; + } + + return ret; +} + static int ep_eventpoll_release(struct inode *inode, struct file *file) { struct eventpoll *ep =3D file->private_data; @@ -975,6 +1041,8 @@ static const struct file_operations eventpoll_fops =3D= { .release =3D ep_eventpoll_release, .poll =3D ep_eventpoll_poll, .llseek =3D noop_llseek, + .unlocked_ioctl =3D ep_eventpoll_ioctl, + .compat_ioctl =3D compat_ptr_ioctl, }; =20 /* diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h index cfbcc4cc49ac..98e5ea525dd0 100644 --- a/include/uapi/linux/eventpoll.h +++ b/include/uapi/linux/eventpoll.h @@ -85,4 +85,16 @@ struct epoll_event { __u64 data; } EPOLL_PACKED; =20 +struct epoll_params { + __aligned_u64 busy_poll_usecs; + __u16 busy_poll_budget; + + /* pad the struct to a multiple of 64bits for alignment on all arches */ + __u8 __pad[6]; +}; + +#define EPOLL_IOC_TYPE 0x8A +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params) +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params) + #endif /* _UAPI_LINUX_EVENTPOLL_H */ --=20 2.25.1