Subject: Re: [RFC] csum experts, csum_replace2() is too expensive

From: Andi Kleen <[email-masked]>
Date: Fri, 21 Mar 2014 14:28:20 +0100

On Fri, Mar 21, 2014 at 05:50:50AM -0700, Eric Dumazet wrote:
> On Thu, 2014-03-20 at 18:56 -0700, Andi Kleen wrote:
> > Eric Dumazet <[email-masked]> writes:
> > >
> > > I saw csum_partial() consuming 1% of cpu cycles in a GRO workload, that
> > > is insane...
> > 
> > 
> > Couldn't it just be the cache miss?
> 
> Or the fact that we mix 16 bit stores and 32bit loads ?

It should cause a small stall from not doing load-store
forwarding, but 1% of a serious workload would be surprising.

Are you sure it's not some skid effect?

-Andi