From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: brouer@redhat.com, netdev@vger.kernel.org
Subject: Re: [PATCH bpf-next 05/11] bpf: avoid retpoline for lookup/update/delete calls on maps
Date: Tue, 29 May 2018 19:23:24 +0200 [thread overview]
Message-ID: <20180529192324.7a1db7ee@redhat.com> (raw)
In-Reply-To: <20180528004344.3606-6-daniel@iogearbox.net>
On Mon, 28 May 2018 02:43:38 +0200
Daniel Borkmann <daniel@iogearbox.net> wrote:
> While some of the BPF map lookup helpers provide a ->map_gen_lookup()
> callback for inlining the map lookup altogether it is not available
> for every map, so the remaining ones have to call bpf_map_lookup_elem()
> helper which does a dispatch to map->ops->map_lookup_elem(). In
> times of retpolines, this will control and trap speculative execution
> rather than letting it do its work for the indirect call and will
> therefore cause a slowdown. Likewise, bpf_map_update_elem() and
> bpf_map_delete_elem() do not have an inlined version and need to call
> into their map->ops->map_update_elem() resp. map->ops->map_delete_elem()
> handlers.
>
> Before:
>
> # bpftool p d x i 1
I would really appreciate if we can use the long options in these kind
of examples. It makes the command "self-documenting" and searchable by
google.
Here it would be:
# bpftool prog dump xlated id 1
> 0: (bf) r2 = r10
> 1: (07) r2 += -8
> 2: (7a) *(u64 *)(r2 +0) = 0
> 3: (18) r1 = map[id:1]
> 5: (85) call __htab_map_lookup_elem#232656
> 6: (15) if r0 == 0x0 goto pc+4
> 7: (71) r1 = *(u8 *)(r0 +35)
> 8: (55) if r1 != 0x0 goto pc+1
> 9: (72) *(u8 *)(r0 +35) = 1
> 10: (07) r0 += 56
> 11: (15) if r0 == 0x0 goto pc+4
> 12: (bf) r2 = r0
> 13: (18) r1 = map[id:1]
> 15: (85) call bpf_map_delete_elem#215008 <-- indirect call via
> 16: (95) exit helper
>
> After:
>
> # bpftool p d x i 1
Same here
> 0: (bf) r2 = r10
> 1: (07) r2 += -8
> 2: (7a) *(u64 *)(r2 +0) = 0
> 3: (18) r1 = map[id:1]
> 5: (85) call __htab_map_lookup_elem#233328
> 6: (15) if r0 == 0x0 goto pc+4
> 7: (71) r1 = *(u8 *)(r0 +35)
> 8: (55) if r1 != 0x0 goto pc+1
> 9: (72) *(u8 *)(r0 +35) = 1
> 10: (07) r0 += 56
> 11: (15) if r0 == 0x0 goto pc+4
> 12: (bf) r2 = r0
> 13: (18) r1 = map[id:1]
> 15: (85) call htab_lru_map_delete_elem#238240 <-- direct call
> 16: (95) exit
>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2018-05-29 17:23 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-28 0:43 [PATCH bpf-next 00/11] Misc BPF improvements Daniel Borkmann
2018-05-28 0:43 ` [PATCH bpf-next 01/11] bpf: test case for map pointer poison with calls/branches Daniel Borkmann
2018-05-29 18:01 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 02/11] bpf: add also cbpf long jump test cases with heavy expansion Daniel Borkmann
2018-05-29 18:09 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 03/11] bpf: fixup error message from gpl helpers on license mismatch Daniel Borkmann
2018-05-29 17:16 ` Jesper Dangaard Brouer
2018-05-29 18:10 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 04/11] bpf: show prog and map id in fdinfo Daniel Borkmann
2018-05-29 17:27 ` Jesper Dangaard Brouer
2018-05-29 19:55 ` Daniel Borkmann
2018-05-30 16:15 ` Song Liu
2018-05-30 17:15 ` Jesper Dangaard Brouer
2018-05-28 0:43 ` [PATCH bpf-next 05/11] bpf: avoid retpoline for lookup/update/delete calls on maps Daniel Borkmann
2018-05-29 17:23 ` Jesper Dangaard Brouer [this message]
2018-05-30 17:06 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 06/11] bpf: add bpf_skb_cgroup_id helper Daniel Borkmann
2018-05-29 12:15 ` Quentin Monnet
2018-05-29 15:43 ` Daniel Borkmann
2018-05-28 0:43 ` [PATCH bpf-next 07/11] bpf: make sure to clear unused fields in tunnel/xfrm state fetch Daniel Borkmann
2018-05-30 17:15 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 08/11] bpf: fix cbpf parser bug for octal numbers Daniel Borkmann
2018-05-30 17:16 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 09/11] bpf: fix context access in tracing progs on 32 bit archs Daniel Borkmann
2018-05-30 16:46 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 10/11] bpf: sync bpf uapi header with tools Daniel Borkmann
2018-05-30 16:10 ` Song Liu
2018-05-28 0:43 ` [PATCH bpf-next 11/11] bpf, doc: add missing patchwork url and libbpf to maintainers Daniel Borkmann
2018-05-30 0:16 ` Song Liu
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