From: Eric Dumazet <eric.dumazet@gmail.com>
To: Daniel Borkmann <daniel@iogearbox.net>, alexei.starovoitov@gmail.com
Cc: peterz@infradead.org, netdev@vger.kernel.org,
bpf@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH bpf] bpf: avoid setting bpf insns pages read-only when prog is jited
Date: Fri, 29 Nov 2019 17:37:57 -0800 [thread overview]
Message-ID: <ec8264ad-8806-208a-1375-51e7cad1866e@gmail.com> (raw)
In-Reply-To: <20191129222911.3710-1-daniel@iogearbox.net>
On 11/29/19 2:29 PM, Daniel Borkmann wrote:
> For the case where the interpreter is compiled out or when the prog is jited
> it is completely unnecessary to set the BPF insn pages as read-only. In fact,
> on frequent churn of BPF programs, it could lead to performance degradation of
> the system over time since it would break the direct map down to 4k pages when
> calling set_memory_ro() for the insn buffer on x86-64 / arm64 and there is no
> reverse operation. Thus, avoid breaking up large pages for data maps, and only
> limit this to the module range used by the JIT where it is necessary to set
> the image read-only and executable.
Interesting... But why the non JIT case would need RO protection ?
Do you have any performance measures to share ?
Thanks.
next prev parent reply other threads:[~2019-11-30 1:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 22:29 [PATCH bpf] bpf: avoid setting bpf insns pages read-only when prog is jited Daniel Borkmann
2019-11-30 1:37 ` Eric Dumazet [this message]
2019-11-30 9:52 ` Daniel Borkmann
2019-12-01 17:54 ` Alexei Starovoitov
2019-12-02 2:49 ` Eric Dumazet
2019-12-02 3:44 ` hpa
2019-12-02 8:30 ` Peter Zijlstra
2019-12-02 9:17 ` Daniel Borkmann
2019-12-02 16:19 ` Alexei Starovoitov
2019-12-02 20:09 ` Daniel Borkmann
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