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From: Song Liu <songliubraving@fb.com>
To: Andrii Nakryiko <andriin@fb.com>
Cc: bpf <bpf@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	"andrii.nakryiko@gmail.com" <andrii.nakryiko@gmail.com>,
	Kernel Team <Kernel-team@fb.com>, Rik van Riel <riel@surriel.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH v2 bpf-next 1/3] bpf: add mmap() support for BPF_MAP_TYPE_ARRAY
Date: Mon, 11 Nov 2019 16:40:29 +0000	[thread overview]
Message-ID: <D7B3FE47-B8E6-4FDB-BB69-F8E3475FCBDA@fb.com> (raw)
In-Reply-To: <20191109080633.2855561-2-andriin@fb.com>



> On Nov 9, 2019, at 12:06 AM, Andrii Nakryiko <andriin@fb.com> wrote:
> 
> Add ability to memory-map contents of BPF array map. This is extremely useful
> for working with BPF global data from userspace programs. It allows to avoid
> typical bpf_map_{lookup,update}_elem operations, improving both performance
> and usability.

[...]

> 
> Generated code for memory-mapped array:
> 
> ; p = bpf_map_lookup_elem(&data_map, &zero);
>  22: (18) r1 = map[id:27]
>  24: (07) r1 += 400			/* array->data offset */
>  25: (79) r1 = *(u64 *)(r1 +0)		/* extra dereference */
>  26: (61) r0 = *(u32 *)(r2 +0)
>  27: (35) if r0 >= 0x3 goto pc+3
>  28: (67) r0 <<= 3
>  29: (0f) r0 += r1
>  30: (05) goto pc+1
>  31: (b7) r0 = 0
> 
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>

Acked-by: Song Liu <songliubraving@fb.com>

  reply	other threads:[~2019-11-11 16:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-09  8:06 [PATCH v2 bpf-next 0/3] Add support for memory-mapping BPF array maps Andrii Nakryiko
2019-11-09  8:06 ` [PATCH v2 bpf-next 1/3] bpf: add mmap() support for BPF_MAP_TYPE_ARRAY Andrii Nakryiko
2019-11-11 16:40   ` Song Liu [this message]
2019-11-11 18:37   ` Jakub Kicinski
2019-11-12  2:06     ` Andrii Nakryiko
2019-11-12 19:17       ` Jakub Kicinski
2019-11-12 22:03         ` Andrii Nakryiko
2019-11-12 22:38           ` Jakub Kicinski
2019-11-13  3:19             ` Andrii Nakryiko
2019-11-11 18:39   ` Jakub Kicinski
2019-11-12  2:01     ` Andrii Nakryiko
2019-11-09  8:06 ` [PATCH v2 bpf-next 2/3] libbpf: make global data internal arrays mmap()-able, if possible Andrii Nakryiko
2019-11-11 18:40   ` Jakub Kicinski
2019-11-12  2:11     ` Andrii Nakryiko
2019-11-09  8:06 ` [PATCH v2 bpf-next 3/3] selftests/bpf: add BPF_TYPE_MAP_ARRAY mmap() tests Andrii Nakryiko

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