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From:   Song Liu <songliubraving@meta.com>
To:     David Vernet <void@manifault.com>
CC:     bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        "martin.lau@linux.dev" <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>,
        Yonghong Song <yonghong.song@linux.dev>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
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        "himadrispandya@gmail.com" <himadrispandya@gmail.com>,
        "julia.lawall@inria.fr" <julia.lawall@inria.fr>
Subject: Re: [PATCH bpf-next 1/2] bpf: Add ability to pin bpf timer to calling
 CPU
Thread-Topic: [PATCH bpf-next 1/2] bpf: Add ability to pin bpf timer to
 calling CPU
Thread-Index: AQHZ9YrG6rN4k0wE80SYLdmAMGheD7A4XaeA
Date:   Tue, 3 Oct 2023 18:06:55 +0000
Message-ID: <F23E4B79-8FEB-4398-8C12-EAEACDE4AE1B@fb.com>
References: <20231002234708.331192-1-void@manifault.com>
In-Reply-To: <20231002234708.331192-1-void@manifault.com>
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> On Oct 2, 2023, at 4:47 PM, David Vernet <void@manifault.com> 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.
> 
> Signed-off-by: David Vernet <void@manifault.com>

Acked-by: Song Liu <song@kernel.org>