linux-kernel - Re: [RFC PATCH 00/11] bpf, trace, dtrace: DTrace BPF program type implementation and sample use

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Date:   Wed, 22 May 2019 14:22:15 -0400
From:   Kris Van Hees <kris.van.hees@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Kris Van Hees <kris.van.hees@...cle.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        dtrace-devel@....oracle.com, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, acme@...nel.org,
        ast@...nel.org, daniel@...earbox.net
Subject: Re: [RFC PATCH 00/11] bpf, trace, dtrace: DTrace BPF program type
 implementation and sample use

On Wed, May 22, 2019 at 04:25:32PM +0200, Peter Zijlstra wrote:
> On Tue, May 21, 2019 at 10:56:18AM -0700, Alexei Starovoitov wrote:
> 
> > and no changes are necessary in kernel/events/ring_buffer.c either.
> 
> Let me just NAK them on the principle that I don't see them in my inbox.

My apologies for failing to include you on the Cc for the patches.  That was
an oversight on my end and certainly not intentional.

> Let me further NAK it for adding all sorts of garbage to the code --
> we're not going to do gaps and stay_in_page nonsense.

Could you give some guidance in terms of an alternative?  The ring buffer code
provides both non-contiguous page allocation support and a vmalloc-based
allocation, and the vmalloc version certainly would avoid the entire gap and
page boundary stuff.  But since the allocator is chosen at build time based on
the arch capabilities, there is no way to select a specific memory allocator.
I'd be happy to use an alternative approach that allows direct writing into
the ring buffer.

	Thanks,
	Kris