From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [net-next PATCH 1/3] Revert "icmp: avoid allocating large
 struct on stack"
Date: Mon, 09 Jan 2017 09:50:08 -0800
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Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>
To: Cong Wang <xiyou.wangcong@gmail.com>
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On Mon, 2017-01-09 at 09:42 -0800, Cong Wang wrote:
> On Mon, Jan 9, 2017 at 7:04 AM, Jesper Dangaard Brouer
> <brouer@redhat.com> wrote:
> > This reverts commit 9a99d4a50cb8 ("icmp: avoid allocating large struct
> > on stack"), because struct icmp_bxm no really a large struct, and
> > allocating and free of this small 112 bytes hurts performance.
> 
> The original commit fixes a warning for large stack usage, icmp_send()
> is deep in the call stack.
> 
> Your optimization for a slow path makes no sense to me.

Do you have the stack trace of this event ?

Even Linus allowed vmalloc() kernel stacks, while it certainly was an
heresy 10 years ago.

I doubt it makes a difference trying to save 104 bytes of kernel stack.