netdev - Re: [PATCH][v3] i40e: optimise prefetch page refcount

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Date:   Tue, 18 Aug 2020 11:19:26 -0700
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     Li RongQing <lirongqing@...du.com>
Cc:     <netdev@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [PATCH][v3] i40e: optimise prefetch page refcount

On Tue, 18 Aug 2020 15:07:57 +0800
Li RongQing <lirongqing@...du.com> wrote:

> refcount of rx_buffer page will be added here originally, so prefetchw
> is needed, but after commit 1793668c3b8c ("i40e/i40evf: Update code to
>  better handle incrementing page count"), and refcount is not added
> everytime, so change prefetchw as prefetch,
> 
> now it mainly services page_address(), but which accesses struct page
> only when WANT_PAGE_VIRTUAL or HASHED_PAGE_VIRTUAL is defined
> otherwise it returns address based on offset, so we prefetch it
> conditionally
> 
> Jakub suggested to define prefetch_page_address in a common header
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Suggested-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Li RongQing <lirongqing@...du.com>

This change looks fine to me, hopefully the more heavyweight
prefetch instruction doesn't impact performance. Were you able to test
any performance?

Reviewed-by: Jesse Brandeburg <jesse.brandeburg@...el.com>