Re: [net-next PATCH 1/3] Revert "icmp: avoid allocating large struct on stack"

On Mon, Jan 9, 2017 at 9:50 AM, Eric Dumazet [off-list ref] wrote:

On Mon, 2017-01-09 at 09:42 -0800, Cong Wang wrote:

quoted

On Mon, Jan 9, 2017 at 7:04 AM, Jesper Dangaard Brouer
[off-list ref] wrote:

quoted

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.

I think you should have known this, quote from Eric Dumazet
(hopefully the same one):

    On Fri, 2013-05-31 at 22:22 -0700, Eric Dumazet wrote:

    Strange, I posted a patch like that some days ago.

which is from: https://patchwork.ozlabs.org/patch/248051/

Facepalm...