Greetings:
Welcome to v6.
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
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 | 136 +++++++++++++++++-
include/uapi/linux/eventpoll.h | 13 ++
3 files changed, 144 insertions(+), 6 deletions(-)
--
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 <= u32_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]>
---
.../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 a69ee11682b9..8eb4ea2557af 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>
/*
@@ -497,6 +498,50 @@ 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;
+ struct epoll_params epoll_params;
+ void __user *uarg = (void __user *) arg;
+
+ ep = 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.prefer_busy_poll > 1)
+ return -EINVAL;
+
+ if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
+ !capable(CAP_NET_ADMIN))
+ return -EPERM;
+
+ ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
+ ep->busy_poll_budget = epoll_params.busy_poll_budget;
+ 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 = ep->busy_poll_usecs;
+ epoll_params.busy_poll_budget = ep->busy_poll_budget;
+ epoll_params.prefer_busy_poll = 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)
@@ -512,6 +557,12 @@ static inline bool ep_busy_loop_on(struct eventpoll *ep)
{
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 */
/*
@@ -871,6 +922,26 @@ 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;
@@ -977,6 +1048,8 @@ 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..36a002660955 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 {
+ __aligned_u64 busy_poll_usecs;
+ __u16 busy_poll_budget;
+ __u8 prefer_busy_poll;
+
+ /* pad the struct to a multiple of 64bits for alignment on all arches */
+ __u8 __pad[5];
+};
+
+#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 02/05, Joe Damato wrote:
> Greetings:
>
> Welcome to v6.
>
> 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
>
> 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 | 136 +++++++++++++++++-
> include/uapi/linux/eventpoll.h | 13 ++
> 3 files changed, 144 insertions(+), 6 deletions(-)
Coincidentally, we were looking into the same area and your patches are
super useful :-) Thank you for plumbing in prefer_busy_poll.
Acked-by: Stanislav Fomichev <[email protected]>
On 05. 02. 24, 22:04, Joe Damato 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 <= u32_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]>
..
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
..
> @@ -497,6 +498,50 @@ 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;
> + struct epoll_params epoll_params;
> + void __user *uarg = (void __user *) arg;
> +
> + ep = file->private_data;
This might have been on the ep declaration line.
> + 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.prefer_busy_poll > 1)
> + return -EINVAL;
> +
> + if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
> + !capable(CAP_NET_ADMIN))
> + return -EPERM;
> +
> + ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> + ep->busy_poll_budget = epoll_params.busy_poll_budget;
> + ep->prefer_busy_poll = !!epoll_params.prefer_busy_poll;
This !! is unnecessary. Nonzero values shall be "converted" to true.
But FWIW, the above is nothing which should be blocking, so:
Reviewed-by: Jiri Slaby <[email protected]>
> + return 0;
> + case EPIOCGPARAMS:
> + memset(&epoll_params, 0, sizeof(epoll_params));
> + epoll_params.busy_poll_usecs = ep->busy_poll_usecs;
> + epoll_params.busy_poll_budget = ep->busy_poll_budget;
> + epoll_params.prefer_busy_poll = ep->prefer_busy_poll;
> + if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params)))
> + return -EFAULT;
> + return 0;
> + default:
> + return -ENOIOCTLCMD;
> + }
> +}
..
thanks,
--
js
suse labs
On Wed, Feb 07, 2024 at 09:37:14AM +0100, Jiri Slaby wrote:
> On 05. 02. 24, 22:04, Joe Damato 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 <= u32_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]>
> ...
> >--- a/fs/eventpoll.c
> >+++ b/fs/eventpoll.c
> ...
> >@@ -497,6 +498,50 @@ 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;
> >+ struct epoll_params epoll_params;
> >+ void __user *uarg = (void __user *) arg;
> >+
> >+ ep = file->private_data;
>
> This might have been on the ep declaration line.
>
> >+ 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.prefer_busy_poll > 1)
> >+ return -EINVAL;
> >+
> >+ if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT &&
> >+ !capable(CAP_NET_ADMIN))
> >+ return -EPERM;
> >+
> >+ ep->busy_poll_usecs = epoll_params.busy_poll_usecs;
> >+ ep->busy_poll_budget = epoll_params.busy_poll_budget;
> >+ ep->prefer_busy_poll = !!epoll_params.prefer_busy_poll;
>
> This !! is unnecessary. Nonzero values shall be "converted" to true.
>
> But FWIW, the above is nothing which should be blocking, so:
">
> Reviewed-by: Jiri Slaby <[email protected]>
netdev maintainers: Jiri marked this with Reviewed-by, but was this review
what caused "Changes Requested" to be the status set for this patch set in
patchwork?
If needed, I'll send a v7 with the changes Jiri suggested and add the
"Reviewed-by" since the changes are cosmetic, but I wanted to make sure
this was the reason.
Thanks.
On Wed, 7 Feb 2024 10:50:15 -0800 Joe Damato wrote:
> > This !! is unnecessary. Nonzero values shall be "converted" to true.
> >
> > But FWIW, the above is nothing which should be blocking, so:
> ">
> > Reviewed-by: Jiri Slaby <[email protected]>
>
> netdev maintainers: Jiri marked this with Reviewed-by, but was this review
> what caused "Changes Requested" to be the status set for this patch set in
> patchwork?
>
> If needed, I'll send a v7 with the changes Jiri suggested and add the
> "Reviewed-by" since the changes are cosmetic, but I wanted to make sure
> this was the reason.
Yes, I think that's it.
On Wed, Feb 07, 2024 at 11:07:26AM -0800, Jakub Kicinski wrote:
> On Wed, 7 Feb 2024 10:50:15 -0800 Joe Damato wrote:
> > > This !! is unnecessary. Nonzero values shall be "converted" to true.
> > >
> > > But FWIW, the above is nothing which should be blocking, so:
> > ">
> > > Reviewed-by: Jiri Slaby <[email protected]>
> >
> > netdev maintainers: Jiri marked this with Reviewed-by, but was this review
> > what caused "Changes Requested" to be the status set for this patch set in
> > patchwork?
> >
> > If needed, I'll send a v7 with the changes Jiri suggested and add the
> > "Reviewed-by" since the changes are cosmetic, but I wanted to make sure
> > this was the reason.
>
> Yes, I think that's it.
OK, thanks for letting me know. I wasn't sure if it was because of the
netdev/source_inline which marked 1/4 as "fail" because of the inlines
added.
Does that need to be changed, as well?
On Wed, 7 Feb 2024 11:16:03 -0800 Joe Damato wrote:
> > > netdev maintainers: Jiri marked this with Reviewed-by, but was this review
> > > what caused "Changes Requested" to be the status set for this patch set in
> > > patchwork?
> > >
> > > If needed, I'll send a v7 with the changes Jiri suggested and add the
> > > "Reviewed-by" since the changes are cosmetic, but I wanted to make sure
> > > this was the reason.
> >
> > Yes, I think that's it.
>
> OK, thanks for letting me know. I wasn't sure if it was because of the
> netdev/source_inline which marked 1/4 as "fail" because of the inlines
> added.
>
> Does that need to be changed, as well?
For background our preference is to avoid using static inline in C
sources, unless the author compiled the code and actually confirmed
the code doesn't get inlined correctly. But it's not a hard
requirement, and technically the code is under fs/.
In general the patchwork checks are a bit noisy, see here the top left
graph of how many of the patches we merge are "all green":
https://netdev.bots.linux.dev/checks.html
Some of the checks are also largely outside of our control (checkpatch)
so consider the patchwork checks as automation for maintainers.
The maintainers should respond on the list if any of the failures
are indeed legit.