BPF supports creating high resolution timers using bpf_timer_* helper
functions. Currently, only the BPF_F_TIMER_ABS flag is supported, which
specifies that the timeout should be interpreted as absolute time. It
would also be useful to be able to pin that timer to a core. For
example, if you wanted to make a subset of cores run without timer
interrupts, and only have the timer be invoked on a single core.
This patch set adds support for this with a new BPF_F_TIMER_CPU_PIN
flag. When specified, the HRTIMER_MODE_PINNED flag is passed to
hrtimer_start().
This patch set is based off of commit 93fb2776f43e ("Merge branch
'bpf-xsk-sh-umem'").
---
v1: https://lore.kernel.org/bpf/[email protected]/
v1 -> v2 changes:
- Put declaration of soft_timer_pinned and abs_timer_pinned selftest
maps on same line as abs_timer (Song)
David Vernet (2):
bpf: Add ability to pin bpf timer to calling CPU
bpf/selftests: Test pinning bpf timer to a core
include/uapi/linux/bpf.h | 4 ++
kernel/bpf/helpers.c | 5 +-
tools/include/uapi/linux/bpf.h | 4 ++
.../testing/selftests/bpf/prog_tests/timer.c | 4 ++
tools/testing/selftests/bpf/progs/timer.c | 63 ++++++++++++++++++-
5 files changed, 78 insertions(+), 2 deletions(-)
--
2.41.0
BPF supports creating high resolution timers using bpf_timer_* helper
functions. Currently, only the BPF_F_TIMER_ABS flag is supported, which
specifies that the timeout should be interpreted as absolute time. It
would also be useful to be able to pin that timer to a core. For
example, if you wanted to make a subset of cores run without timer
interrupts, and only have the timer be invoked on a single core.
This patch adds support for this with a new BPF_F_TIMER_CPU_PIN flag.
When specified, the HRTIMER_MODE_PINNED flag is passed to
hrtimer_start(). A subsequent patch will update selftests to validate.
Acked-by: Song Liu <[email protected]>
Signed-off-by: David Vernet <[email protected]>
---
include/uapi/linux/bpf.h | 4 ++++
kernel/bpf/helpers.c | 5 ++++-
tools/include/uapi/linux/bpf.h | 4 ++++
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 70bfa997e896..a7d4a1a69f21 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5096,6 +5096,8 @@ union bpf_attr {
* **BPF_F_TIMER_ABS**
* Start the timer in absolute expire value instead of the
* default relative one.
+ * **BPF_F_TIMER_CPU_PIN**
+ * Timer will be pinned to the CPU of the caller.
*
* Return
* 0 on success.
@@ -7309,9 +7311,11 @@ struct bpf_core_relo {
* Flags to control bpf_timer_start() behaviour.
* - BPF_F_TIMER_ABS: Timeout passed is absolute time, by default it is
* relative to current time.
+ * - BPF_F_TIMER_CPU_PIN: Timer will be pinned to the CPU of the caller.
*/
enum {
BPF_F_TIMER_ABS = (1ULL << 0),
+ BPF_F_TIMER_CPU_PIN = (1ULL << 1),
};
/* BPF numbers iterator state */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index dd1c69ee3375..d2840dd5b00d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1272,7 +1272,7 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
if (in_nmi())
return -EOPNOTSUPP;
- if (flags > BPF_F_TIMER_ABS)
+ if (flags & ~(BPF_F_TIMER_ABS | BPF_F_TIMER_CPU_PIN))
return -EINVAL;
__bpf_spin_lock_irqsave(&timer->lock);
t = timer->timer;
@@ -1286,6 +1286,9 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
else
mode = HRTIMER_MODE_REL_SOFT;
+ if (flags & BPF_F_TIMER_CPU_PIN)
+ mode |= HRTIMER_MODE_PINNED;
+
hrtimer_start(&t->timer, ns_to_ktime(nsecs), mode);
out:
__bpf_spin_unlock_irqrestore(&timer->lock);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 70bfa997e896..a7d4a1a69f21 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5096,6 +5096,8 @@ union bpf_attr {
* **BPF_F_TIMER_ABS**
* Start the timer in absolute expire value instead of the
* default relative one.
+ * **BPF_F_TIMER_CPU_PIN**
+ * Timer will be pinned to the CPU of the caller.
*
* Return
* 0 on success.
@@ -7309,9 +7311,11 @@ struct bpf_core_relo {
* Flags to control bpf_timer_start() behaviour.
* - BPF_F_TIMER_ABS: Timeout passed is absolute time, by default it is
* relative to current time.
+ * - BPF_F_TIMER_CPU_PIN: Timer will be pinned to the CPU of the caller.
*/
enum {
BPF_F_TIMER_ABS = (1ULL << 0),
+ BPF_F_TIMER_CPU_PIN = (1ULL << 1),
};
/* BPF numbers iterator state */
--
2.41.0
On 10/5/2023 12:23 AM, David Vernet wrote:
> BPF supports creating high resolution timers using bpf_timer_* helper
> functions. Currently, only the BPF_F_TIMER_ABS flag is supported, which
> specifies that the timeout should be interpreted as absolute time. It
> would also be useful to be able to pin that timer to a core. For
> example, if you wanted to make a subset of cores run without timer
> interrupts, and only have the timer be invoked on a single core.
>
> This patch adds support for this with a new BPF_F_TIMER_CPU_PIN flag.
> When specified, the HRTIMER_MODE_PINNED flag is passed to
> hrtimer_start(). A subsequent patch will update selftests to validate.
>
> Acked-by: Song Liu <[email protected]>
> Signed-off-by: David Vernet <[email protected]>
Acked-by: Hou Tao <[email protected]>
Hello:
This series was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:
On Wed, 4 Oct 2023 11:23:37 -0500 you wrote:
> BPF supports creating high resolution timers using bpf_timer_* helper
> functions. Currently, only the BPF_F_TIMER_ABS flag is supported, which
> specifies that the timeout should be interpreted as absolute time. It
> would also be useful to be able to pin that timer to a core. For
> example, if you wanted to make a subset of cores run without timer
> interrupts, and only have the timer be invoked on a single core.
>
> [...]
Here is the summary with links:
- [bpf-next,v2,1/2] bpf: Add ability to pin bpf timer to calling CPU
https://git.kernel.org/bpf/bpf-next/c/d6247ecb6c1e
- [bpf-next,v2,2/2] bpf/selftests: Test pinning bpf timer to a core
https://git.kernel.org/bpf/bpf-next/c/0d7ae0686075
You are awesome, thank you!
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