From: David Laight <David.Laight@ACULAB.COM>
To: "'Björn Töpel'" <bjorn.topel@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"ast@kernel.org" <ast@kernel.org>,
"daniel@iogearbox.net" <daniel@iogearbox.net>
Cc: "Björn Töpel" <bjorn.topel@intel.com>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"magnus.karlsson@gmail.com" <magnus.karlsson@gmail.com>,
"magnus.karlsson@intel.com" <magnus.karlsson@intel.com>,
"jonathan.lemon@gmail.com" <jonathan.lemon@gmail.com>,
"ecree@solarflare.com" <ecree@solarflare.com>,
"thoiland@redhat.com" <thoiland@redhat.com>,
"brouer@redhat.com" <brouer@redhat.com>,
"andrii.nakryiko@gmail.com" <andrii.nakryiko@gmail.com>
Subject: RE: [PATCH bpf-next v5 6/6] bpf, x86: align dispatcher branch targets to 16B
Date: Mon, 16 Dec 2019 16:45:35 +0000 [thread overview]
Message-ID: <1cb77c2dcfeb495c9e7c417edd7f43cc@AcuMS.aculab.com> (raw)
In-Reply-To: <20191213175112.30208-7-bjorn.topel@gmail.com>
From: Björn Töpel
> Sent: 13 December 2019 17:51
> From: Björn Töpel <bjorn.topel@intel.com>
>
> From Intel 64 and IA-32 Architectures Optimization Reference Manual,
> 3.4.1.4 Code Alignment, Assembly/Compiler Coding Rule 11: All branch
> targets should be 16-byte aligned.
>
> This commits aligns branch targets according to the Intel manual.
I'd Ignore that advice....
It makes very little difference, and none at all on more recent cpu.
Read https://www.agner.org/optimize/microarchitecture.pdf
The extra cache footprint probably makes a bigger difference.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2019-12-16 16:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-13 17:51 [PATCH bpf-next v5 0/6] Introduce the BPF dispatcher Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 1/6] bpf: move trampoline JIT image allocation to a function Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 2/6] bpf: introduce BPF dispatcher Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 3/6] bpf, xdp: start using the BPF dispatcher for XDP Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 4/6] bpf: start using the BPF dispatcher in BPF_TEST_RUN Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 5/6] selftests: bpf: add xdp_perf test Björn Töpel
2019-12-13 17:51 ` [PATCH bpf-next v5 6/6] bpf, x86: align dispatcher branch targets to 16B Björn Töpel
2019-12-16 16:45 ` David Laight [this message]
2019-12-13 21:23 ` [PATCH bpf-next v5 0/6] Introduce the BPF dispatcher Alexei Starovoitov
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