From: David Vernet <void@manifault.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, jolsa@kernel.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: [PATCH bpf-next v2 1/2] bpf: Add ability to pin bpf timer to calling CPU
Date: Wed, 4 Oct 2023 11:23:38 -0500 [thread overview]
Message-ID: <20231004162339.200702-2-void@manifault.com> (raw)
In-Reply-To: <20231004162339.200702-1-void@manifault.com>
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 <song@kernel.org>
Signed-off-by: David Vernet <void@manifault.com>
---
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
next prev parent reply other threads:[~2023-10-04 16:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-04 16:23 [PATCH bpf-next v2 0/2] bpf: Add ability to pin bpf timer to calling CPU David Vernet
2023-10-04 16:23 ` David Vernet [this message]
2023-10-08 4:09 ` [PATCH bpf-next v2 1/2] " Hou Tao
2023-10-04 16:23 ` [PATCH bpf-next v2 2/2] bpf/selftests: Test pinning bpf timer to a core David Vernet
2023-10-08 4:23 ` Hou Tao
2023-10-09 14:40 ` [PATCH bpf-next v2 0/2] bpf: Add ability to pin bpf timer to calling CPU patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20231004162339.200702-2-void@manifault.com \
--to=void@manifault.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=haoluo@google.com \
--cc=john.fastabend@gmail.com \
--cc=jolsa@kernel.org \
--cc=kernel-team@meta.com \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=martin.lau@linux.dev \
--cc=sdf@google.com \
--cc=song@kernel.org \
--cc=yonghong.song@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).