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SubjectRe: [Linux-kernel-mentees][PATCH 0/2] reorder members of structures in virtio_net for optimization
On Fri, Oct 02, 2020 at 07:06:38PM -0700, David Miller wrote:
> From: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> Date: Wed, 30 Sep 2020 10:47:20 +0530
>
> > The structures virtnet_info and receive_queue have byte holes in
> > middle, and their members could do with some rearranging
> > (order-of-declaration wise) in order to overcome this.
> >
> > Rearranging the members helps in:
> > * elimination the byte holes in the middle of the structures
> > * reduce the size of the structure (virtnet_info)
> > * have more members stored in one cache line (as opposed to
> > unnecessarily crossing the cacheline boundary and spanning
> > different cachelines)
> >
> > The analysis was performed using pahole.
> >
> > These patches may be applied in any order.
>
> What effects do these changes have on performance?
>
> The cache locality for various TX and RX paths could be effected.
>
> I'm not applying these patches without some data on the performance
> impact.
>
> Thank you.

Agree wholeheartedly.

--
MST

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