From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Hao Luo <haoluo@google.com>,
Daniel Borkmann <daniel@iogearbox.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Stanislav Fomichev <sdf@google.com>,
Jiri Olsa <jolsa@kernel.org>, KP Singh <kpsingh@kernel.org>,
Yonghong Song <yhs@fb.com>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] powerpc/bpf: Only update ldimm64 during extra pass when it is an address
Date: Thu, 24 Nov 2022 12:24:40 +0000 [thread overview]
Message-ID: <9f17237f-94da-f58f-4f4b-0068851b4123@csgroup.eu> (raw)
In-Reply-To: <1669284441.66eunvaboi.naveen@linux.ibm.com>
Le 24/11/2022 à 11:13, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> ldimm64 is not only used for loading function addresses, and
>
> That's probably true today, but I worry that that can change upstream
> and we may not notice at all.
Not sure what you mean.
Today POWERPC considers that ldimm64 is _always_ loading a function
address whereas upstream BPF considers that ldimm64 is a function only
when it is flagged BPF_PSEUDO_FUNC.
In what direction could that change in the future ?
For me if they change that it becomes an API change.
Christophe
>
>> the NOPs added for padding are impacting performance, so avoid
>> them when not necessary.
>>
>> On QEMU mac99, with the patch:
>>
>> test_bpf: #829 ALU64_MOV_K: all immediate value magnitudes jited:1
>> 167436810 PASS
>> test_bpf: #831 ALU64_OR_K: all immediate value magnitudes jited:1
>> 170702940 PASS
>>
>> Without the patch:
>>
>> test_bpf: #829 ALU64_MOV_K: all immediate value magnitudes jited:1
>> 173012360 PASS
>> test_bpf: #831 ALU64_OR_K: all immediate value magnitudes jited:1
>> 176424090 PASS
>>
>> That's a 3.5% performance improvement.
>
> A better approach would be to do a full JIT during the extra pass.
> That's what most other architectures do today. And, as long as we can
> ensure that the JIT'ed program size can never increase during the extra
> pass, we should be ok to do a single extra pass.
>
>
> - Naveen
next prev parent reply other threads:[~2022-11-24 12:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-24 8:39 [PATCH] powerpc/bpf: Only update ldimm64 during extra pass when it is an address Christophe Leroy
2022-11-24 10:13 ` Naveen N. Rao
2022-11-24 12:24 ` Christophe Leroy [this message]
2022-11-24 13:49 ` Naveen N. Rao
2022-11-24 19:46 ` Christophe Leroy
2022-11-25 5:38 ` Naveen N. Rao
2022-11-25 5:59 ` Christophe Leroy
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