linux-kernel - Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in BPF JIT

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Message-ID: <87fs5gguyt.fsf@all.your.base.are.belong.to.us>
Date:   Sat, 22 Jul 2023 11:24:10 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     Puranjay Mohan <puranjay12@...il.com>, paul.walmsley@...ive.com,
        palmer@...belt.com, aou@...s.berkeley.edu, pulehui@...wei.com,
        conor.dooley@...rochip.com, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, kpsingh@...nel.org, bpf@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     puranjay12@...il.com
Subject: Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in
 BPF JIT

Puranjay Mohan <puranjay12@...il.com> writes:

> BPF programs currently consume a page each on RISCV. For systems with many BPF
> programs, this adds significant pressure to instruction TLB. High iTLB pressure
> usually causes slow down for the whole system.
>
> Song Liu introduced the BPF prog pack allocator[1] to mitigate the above issue.
> It packs multiple BPF programs into a single huge page. It is currently only
> enabled for the x86_64 BPF JIT.
>
> I enabled this allocator on the ARM64 BPF JIT[2]. It is being reviewed now.
>
> This patch series enables the BPF prog pack allocator for the RISCV BPF JIT.
> This series needs a patch[3] from the ARM64 series to work.

Just a heads-up; I'm on vacation for 2 more weeks, so expect a somewhat
late review from my side!

Thank you for working on the RISC-V BPF JIT!


Björn