Greetings:
Welcome to v8.
TL;DR This builds on commit bf3b9f6372c4 ("epoll: Add busy poll support to
epoll with socket fds.") by allowing user applications to enable
epoll-based busy polling, set a busy poll packet budget, and enable or
disable prefer busy poll on a per epoll context basis.
This makes epoll-based busy polling much more usable for user
applications than the current system-wide sysctl and hardcoded budget.
To allow for this, two ioctls have been added for epoll contexts for
getting and setting a new struct, struct epoll_params.
ioctl was chosen vs a new syscall after reviewing a suggestion by Willem
de Bruijn [1]. I am open to using a new syscall instead of an ioctl, but it
seemed that:
- Busy poll affects all existing epoll_wait and epoll_pwait variants in
the same way, so new verions of many syscalls might be needed. It
seems much simpler for users to use the correct
epoll_wait/epoll_pwait for their app and add a call to ioctl to enable
or disable busy poll as needed. This also probably means less work to
get an existing epoll app using busy poll.
- previously added epoll_pwait2 helped to bring epoll closer to
existing syscalls (like pselect and ppoll) and this busy poll change
reflected as a new syscall would not have the same effect.
Note: patch 1/4 as of v4 uses an or (||) instead of an xor. I thought about
it some more and I realized that if the user enables both the per-epoll
context setting and the system wide sysctl, then busy poll should be
enabled and not disabled. Using xor doesn't seem to make much sense after
thinking through this a bit.
Longer explanation:
Presently epoll has support for a very useful form of busy poll based on
the incoming NAPI ID (see also: SO_INCOMING_NAPI_ID [2]).
This form of busy poll allows epoll_wait to drive NAPI packet processing
which allows for a few interesting user application designs which can
reduce latency and also potentially improve L2/L3 cache hit rates by
deferring NAPI until userland has finished its work.
The documentation available on this is, IMHO, a bit confusing so please
allow me to explain how one might use this:
1. Ensure each application thread has its own epoll instance mapping
1-to-1 with NIC RX queues. An n-tuple filter would likely be used to
direct connections with specific dest ports to these queues.
2. Optionally: Setup IRQ coalescing for the NIC RX queues where busy
polling will occur. This can help avoid the userland app from being
pre-empted by a hard IRQ while userland is running. Note this means that
userland must take care to call epoll_wait and not take too long in
userland since it now drives NAPI via epoll_wait.
3. Optionally: Consider using napi_defer_hard_irqs and gro_flush_timeout to
further restrict IRQ generation from the NIC. These settings are
system-wide so their impact must be carefully weighed against the running
applications.
4. Ensure that all incoming connections added to an epoll instance
have the same NAPI ID. This can be done with a BPF filter when
SO_REUSEPORT is used or getsockopt + SO_INCOMING_NAPI_ID when a single
accept thread is used which dispatches incoming connections to threads.
5. Lastly, busy poll must be enabled via a sysctl
(/proc/sys/net/core/busy_poll).
Please see Eric Dumazet's paper about busy polling [3] and a recent
academic paper about measured performance improvements of busy polling [4]
(albeit with a modification that is not currently present in the kernel)
for additional context.
The unfortunate part about step 5 above is that this enables busy poll
system-wide which affects all user applications on the system,
including epoll-based network applications which were not intended to
be used this way or applications where increased CPU usage for lower
latency network processing is unnecessary or not desirable.
If the user wants to run one low latency epoll-based server application
with epoll-based busy poll, but would like to run the rest of the
applications on the system (which may also use epoll) without busy poll,
this system-wide sysctl presents a significant problem.
This change preserves the system-wide sysctl, but adds a mechanism (via
ioctl) to enable or disable busy poll for epoll contexts as needed by
individual applications, making epoll-based busy poll more usable.
Note that this change includes an or (as of v4) instead of an xor. If the
user has enabled both the system-wide sysctl and also the per epoll-context
busy poll settings, then epoll should probably busy poll (vs being
disabled).
Thanks,
Joe
v7 -> v8:
- Reviewed-by tag from Eric Dumazet applied to commit message of patch
1/4.
- patch 4/4:
- EPIOCSPARAMS and EPIOCGPARAMS updated to use WRITE_ONCE and
READ_ONCE, as requested by Eric Dumazet
- Wrapped a long line (via netdev/checkpatch)
v6 -> v7:
- Acked-by tags from Stanislav Fomichev applied to commit messages of
all patches.
- Reviewed-by tags from Jakub Kicinski, Eric Dumazet applied to commit
messages of patches 2 and 3. Jiri Slaby's Reviewed-by applied to patch
4.
- patch 1/4:
- busy_poll_usecs reduced from u64 to u32.
- Unnecessary parens removed (via netdev/checkpatch)
- Wrapped long line (via netdev/checkpatch)
- Remove inline from busy_loop_ep_timeout as objdump suggests the
function is already inlined
- Moved struct eventpoll assignment to declaration
- busy_loop_ep_timeout is moved within CONFIG_NET_RX_BUSY_POLL and the
ifdefs internally have been removed as per Eric Dumazet's review
- Removed ep_busy_loop_on from the !defined CONFIG_NET_RX_BUSY_POLL
section as it is only called when CONFIG_NET_RX_BUSY_POLL is
defined
- patch 3/4:
- Fix whitespace alignment issue (via netdev/checkpatch)
- patch 4/4:
- epoll_params.busy_poll_usecs has been reduced to u32
- epoll_params.busy_poll_usecs is now checked to ensure it is <=
S32_MAX
- __pad has been reduced to a single u8
- memchr_inv has been dropped and replaced with a simple check for the
single __pad byte
- Removed space after cast (via netdev/checkpatch)
- Wrap long line (via netdev/checkpatch)
- Move struct eventpoll *ep assignment to declaration as per Jiri
Slaby's review
- Remove unnecessary !! as per Jiri Slaby's review
- Reorganized variables to be reverse christmas tree order
v5 -> v6:
- patch 1/3 no functional change, but commit message corrected to explain
that an or (||) is being used instead of xor.
- patch 3/4 is a new patch which adds support for per epoll context
prefer busy poll setting.
- patch 4/4 updated to allow getting/setting per epoll context prefer
busy poll setting; this setting is limited to either 0 or 1.
v4 -> v5:
- patch 3/3 updated to use memchr_inv to ensure that __pad is zero for
the EPIOCSPARAMS ioctl. Recommended by Greg K-H [5], Dave Chinner [6],
and Jiri Slaby [7].
v3 -> v4:
- patch 1/3 was updated to include an important functional change:
ep_busy_loop_on was updated to use or (||) instead of xor (^). After
thinking about it a bit more, I thought xor didn't make much sense.
Enabling both the per-epoll context and the system-wide sysctl should
probably enable busy poll, not disable it. So, or (||) makes more
sense, I think.
- patch 3/3 was updated:
- to change the epoll_params fields to be __u64, __u16, and __u8 and
to pad the struct to a multiple of 64bits. Suggested by Greg K-H [8]
and Arnd Bergmann [9].
- remove an unused pr_fmt, left over from the previous revision.
- ioctl now returns -EINVAL when epoll_params.busy_poll_usecs >
U32_MAX.
v2 -> v3:
- cover letter updated to mention why ioctl seems (to me) like a better
choice vs a new syscall.
- patch 3/4 was modified in 3 ways:
- when an unknown ioctl is received, -ENOIOCTLCMD is returned instead
of -EINVAL as the ioctl documentation requires.
- epoll_params.busy_poll_budget can only be set to a value larger than
NAPI_POLL_WEIGHT if code is run by privileged (CAP_NET_ADMIN) users.
Otherwise, -EPERM is returned.
- busy poll specific ioctl code moved out to its own function. On
kernels without busy poll support, -EOPNOTSUPP is returned. This also
makes the kernel build robot happier without littering the code with
more #ifdefs.
- dropped patch 4/4 after Eric Dumazet's review of it when it was sent
independently to the list [10].
v1 -> v2:
- cover letter updated to make a mention of napi_defer_hard_irqs and
gro_flush_timeout as an added step 3 and to cite both Eric Dumazet's
busy polling paper and a paper from University of Waterloo for
additional context. Specifically calling out the xor in patch 1/4
incase it is missed by reviewers.
- Patch 2/4 has its commit message updated, but no functional changes.
Commit message now describes that allowing for a settable budget helps
to improve throughput and is more consistent with other busy poll
mechanisms that allow a settable budget via SO_BUSY_POLL_BUDGET.
- Patch 3/4 was modified to check if the epoll_params.busy_poll_budget
exceeds NAPI_POLL_WEIGHT. The larger value is allowed, but an error is
printed. This was done for consistency with netif_napi_add_weight,
which does the same.
- Patch 3/4 the struct epoll_params was updated to fix the type of the
data field; it was uint8_t and was changed to u8.
- Patch 4/4 added to check if SO_BUSY_POLL_BUDGET exceeds
NAPI_POLL_WEIGHT. The larger value is allowed, but an error is
printed. This was done for consistency with netif_napi_add_weight,
which does the same.
[1]: https://lore.kernel.org/lkml/[email protected]/
[2]: https://lore.kernel.org/lkml/[email protected]/
[3]: https://netdevconf.info/2.1/papers/BusyPollingNextGen.pdf
[4]: https://dl.acm.org/doi/pdf/10.1145/3626780
[5]: https://lore.kernel.org/lkml/2024013001-prison-strum-899d@gregkh/
[6]: https://lore.kernel.org/lkml/[email protected]/
[7]: https://lore.kernel.org/lkml/[email protected]/
[8]: https://lore.kernel.org/lkml/2024012551-anyone-demeaning-867b@gregkh/
[9]: https://lore.kernel.org/lkml/[email protected]/
[10]: https://lore.kernel.org/lkml/CANn89i+uXsdSVFiQT9fDfGw+h_5QOcuHwPdWi9J=5U6oLXkQTA@mail.gmail.com/
Joe Damato (4):
eventpoll: support busy poll per epoll instance
eventpoll: Add per-epoll busy poll packet budget
eventpoll: Add per-epoll prefer busy poll option
eventpoll: Add epoll ioctl for epoll_params
.../userspace-api/ioctl/ioctl-number.rst | 1 +
fs/eventpoll.c | 131 +++++++++++++++++-
include/uapi/linux/eventpoll.h | 13 ++
3 files changed, 138 insertions(+), 7 deletions(-)
--
2.25.1
Allow busy polling on a per-epoll context basis. The per-epoll context
usec timeout value is preferred, but the pre-existing system wide sysctl
value is still supported if it specified.
busy_poll_usecs is a u32, but in a follow up patch the ioctl provided to
the user only allows setting a value from 0 to S32_MAX.
Signed-off-by: Joe Damato <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
---
fs/eventpoll.c | 44 +++++++++++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 5 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 3534d36a1474..401f865eced9 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 */
+ u32 busy_poll_usecs;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -387,11 +389,41 @@ static inline int ep_events_available(struct eventpoll *ep)
}
#ifdef CONFIG_NET_RX_BUSY_POLL
+/**
+ * busy_loop_ep_timeout - check if busy poll has timed out. The timeout value
+ * 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 timeout.
+ * @ep: Pointer to the eventpoll context.
+ *
+ * Return: true if the timeout has expired, false otherwise.
+ */
+static bool busy_loop_ep_timeout(unsigned long start_time,
+ struct eventpoll *ep)
+{
+ unsigned long bp_usec = READ_ONCE(ep->busy_poll_usecs);
+
+ if (bp_usec) {
+ unsigned long end_time = start_time + bp_usec;
+ unsigned long now = busy_loop_current_time();
+
+ return time_after(now, end_time);
+ } else {
+ return busy_loop_timeout(start_time);
+ }
+}
+
+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 = p;
- return ep_events_available(ep) || busy_loop_timeout(start_time);
+ return ep_events_available(ep) || busy_loop_ep_timeout(start_time, ep);
}
/*
@@ -404,7 +436,7 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
{
unsigned int napi_id = READ_ONCE(ep->napi_id);
- if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) {
+ 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);
if (ep_events_available(ep))
@@ -425,12 +457,12 @@ static bool ep_busy_loop(struct eventpoll *ep, int nonblock)
*/
static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
{
- struct eventpoll *ep;
+ struct eventpoll *ep = epi->ep;
unsigned int napi_id;
struct socket *sock;
struct sock *sk;
- if (!net_busy_loop_on())
+ if (!ep_busy_loop_on(ep))
return;
sock = sock_from_file(epi->ffd.file);
@@ -442,7 +474,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
return;
napi_id = READ_ONCE(sk->sk_napi_id);
- ep = epi->ep;
/* Non-NAPI IDs can be rejected
* or
@@ -2058,6 +2089,9 @@ static int do_epoll_create(int flags)
error = PTR_ERR(file);
goto out_free_fd;
}
+#ifdef CONFIG_NET_RX_BUSY_POLL
+ ep->busy_poll_usecs = 0;
+#endif
ep->file = file;
fd_install(fd, file);
return fd;
--
2.25.1
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 <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Jakub Kicinski <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
---
fs/eventpoll.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 401f865eced9..ed83ae33dd45 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -229,6 +229,8 @@ struct eventpoll {
unsigned int napi_id;
/* busy poll timeout */
u32 busy_poll_usecs;
+ /* busy poll packet budget */
+ u16 busy_poll_budget;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -435,10 +437,14 @@ 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;
/*
@@ -2091,6 +2097,7 @@ 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
When using epoll-based busy poll, the prefer_busy_poll option is hardcoded
to false. Users may want to enable prefer_busy_poll to be used in
conjunction with gro_flush_timeout and defer_hard_irqs_count to keep device
IRQs masked.
Other busy poll methods allow enabling or disabling prefer busy poll via
SO_PREFER_BUSY_POLL, but epoll-based busy polling uses a hardcoded value.
Fix this edge case by adding support for a per-epoll context
prefer_busy_poll option. The default is false, as it was hardcoded before
this change.
Signed-off-by: Joe Damato <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Jakub Kicinski <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
---
fs/eventpoll.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ed83ae33dd45..1b8d01af0c2c 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -231,6 +231,7 @@ struct eventpoll {
u32 busy_poll_usecs;
/* busy poll packet budget */
u16 busy_poll_budget;
+ bool prefer_busy_poll;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -438,13 +439,14 @@ 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);
+ bool prefer_busy_poll = READ_ONCE(ep->prefer_busy_poll);
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,
- budget);
+ napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end,
+ ep, prefer_busy_poll, budget);
if (ep_events_available(ep))
return true;
/*
@@ -2098,6 +2100,7 @@ static int do_epoll_create(int flags)
#ifdef CONFIG_NET_RX_BUSY_POLL
ep->busy_poll_usecs = 0;
ep->busy_poll_budget = 0;
+ ep->prefer_busy_poll = false;
#endif
ep->file = file;
fd_install(fd, file);
--
2.25.1
Add an ioctl for getting and setting epoll_params. User programs can use
this ioctl to get and set the busy poll usec time, packet budget, and
prefer busy poll params for a specific epoll context.
Parameters are limited:
- busy_poll_usecs is limited to <= s32_max
- busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
users (!capable(CAP_NET_ADMIN))
- prefer_busy_poll must be 0 or 1
- __pad must be 0
Signed-off-by: Joe Damato <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Reviewed-by: Jiri Slaby <[email protected]>
---
.../userspace-api/ioctl/ioctl-number.rst | 1 +
fs/eventpoll.c | 73 +++++++++++++++++++
include/uapi/linux/eventpoll.h | 13 ++++
3 files changed, 87 insertions(+)
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/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 SIOCPROTOPRIVATE range
0x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range
+0x8A 00-1F linux/eventpoll.h
0x8B all linux/wireless.h
0x8C 00-3F WiNRADiO driver
<http://www.winradio.com.au/>
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1b8d01af0c2c..df2ed3af486e 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -37,6 +37,7 @@
#include <linux/seq_file.h>
#include <linux/compat.h>
#include <linux/rculist.h>
+#include <linux/capability.h>
#include <net/busy_poll.h>
/*
@@ -494,6 +495,49 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
ep->napi_id = napi_id;
}
+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ struct eventpoll *ep = file->private_data;
+ void __user *uarg = (void __user *)arg;
+ struct epoll_params epoll_params;
+
+ switch (cmd) {
+ case EPIOCSPARAMS:
+ if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params)))
+ return -EFAULT;
+
+ /* pad byte must be zero */
+ if (epoll_params.__pad)
+ return -EINVAL;
+
+ if (epoll_params.busy_poll_usecs > S32_MAX)
+ return -EINVAL;
+
+ if (epoll_params.prefer_busy_poll > 1)
+ return -EINVAL;
+
+ if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
+ !capable(CAP_NET_ADMIN))
+ return -EPERM;
+
+ WRITE_ONCE(ep->busy_poll_usecs, epoll_params.busy_poll_usecs);
+ WRITE_ONCE(ep->busy_poll_budget, epoll_params.busy_poll_budget);
+ WRITE_ONCE(ep->prefer_busy_poll, epoll_params.prefer_busy_poll);
+ return 0;
+ case EPIOCGPARAMS:
+ memset(&epoll_params, 0, sizeof(epoll_params));
+ epoll_params.busy_poll_usecs = READ_ONCE(ep->busy_poll_usecs);
+ epoll_params.busy_poll_budget = READ_ONCE(ep->busy_poll_budget);
+ epoll_params.prefer_busy_poll = READ_ONCE(ep->prefer_busy_poll);
+ if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
+ return -EFAULT;
+ return 0;
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
#else
static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock)
@@ -505,6 +549,12 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi)
{
}
+static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ return -EOPNOTSUPP;
+}
+
#endif /* CONFIG_NET_RX_BUSY_POLL */
/*
@@ -864,6 +914,27 @@ static void ep_clear_and_put(struct eventpoll *ep)
ep_free(ep);
}
+static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ int ret;
+
+ if (!is_file_epoll(file))
+ return -EINVAL;
+
+ switch (cmd) {
+ case EPIOCSPARAMS:
+ case EPIOCGPARAMS:
+ ret = ep_eventpoll_bp_ioctl(file, cmd, arg);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
static int ep_eventpoll_release(struct inode *inode, struct file *file)
{
struct eventpoll *ep = file->private_data;
@@ -970,6 +1041,8 @@ static const struct file_operations eventpoll_fops = {
.release = ep_eventpoll_release,
.poll = ep_eventpoll_poll,
.llseek = noop_llseek,
+ .unlocked_ioctl = ep_eventpoll_ioctl,
+ .compat_ioctl = compat_ptr_ioctl,
};
/*
diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
index cfbcc4cc49ac..4f4b948ef381 100644
--- a/include/uapi/linux/eventpoll.h
+++ b/include/uapi/linux/eventpoll.h
@@ -85,4 +85,17 @@ struct epoll_event {
__u64 data;
} EPOLL_PACKED;
+struct epoll_params {
+ __u32 busy_poll_usecs;
+ __u16 busy_poll_budget;
+ __u8 prefer_busy_poll;
+
+ /* pad the struct to a multiple of 64bits */
+ __u8 __pad;
+};
+
+#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 */
--
2.25.1
On Tue, Feb 13, 2024 at 7:17 AM Joe Damato <[email protected]> wrote:
>
> Add an ioctl for getting and setting epoll_params. User programs can use
> this ioctl to get and set the busy poll usec time, packet budget, and
> prefer busy poll params for a specific epoll context.
>
> Parameters are limited:
> - busy_poll_usecs is limited to <= s32_max
> - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
> users (!capable(CAP_NET_ADMIN))
> - prefer_busy_poll must be 0 or 1
> - __pad must be 0
>
> Signed-off-by: Joe Damato <[email protected]>
> Acked-by: Stanislav Fomichev <[email protected]>
> Reviewed-by: Jiri Slaby <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Thanks !
Hello:
This series was applied to netdev/net-next.git (main)
by David S. Miller <[email protected]>:
On Tue, 13 Feb 2024 06:16:41 +0000 you wrote:
> Greetings:
>
> Welcome to v8.
>
> TL;DR This builds on commit bf3b9f6372c4 ("epoll: Add busy poll support to
> epoll with socket fds.") by allowing user applications to enable
> epoll-based busy polling, set a busy poll packet budget, and enable or
> disable prefer busy poll on a per epoll context basis.
>
> [...]
Here is the summary with links:
- [net-next,v8,1/4] eventpoll: support busy poll per epoll instance
https://git.kernel.org/netdev/net-next/c/85455c795c07
- [net-next,v8,2/4] eventpoll: Add per-epoll busy poll packet budget
https://git.kernel.org/netdev/net-next/c/c6aa2a7778d8
- [net-next,v8,3/4] eventpoll: Add per-epoll prefer busy poll option
https://git.kernel.org/netdev/net-next/c/de57a2510822
- [net-next,v8,4/4] eventpoll: Add epoll ioctl for epoll_params
https://git.kernel.org/netdev/net-next/c/18e2bf0edf4d
You are awesome, thank you!
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