netdev - Re: [PATCH net-next 1/2] net-zerocopy: Reduce compound page head access

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Date:   Tue, 21 Mar 2023 19:53:26 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Coco Li <lixiaoyan@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Al Viro <viro@...iv.linux.org.uk>, netdev@...r.kernel.org,
        inux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] net-zerocopy: Reduce compound page head access

On Tue, Mar 21, 2023 at 1:12 AM Coco Li <lixiaoyan@...gle.com> wrote:
>
> From: Xiaoyan Li <lixiaoyan@...gle.com>
>
> When compound pages are enabled, although the mm layer still
> returns an array of page pointers, a subset (or all) of them
> may have the same page head since a max 180kb skb can span 2
> hugepages if it is on the boundary, be a mix of pages and 1 hugepage,
> or fit completely in a hugepage. Instead of referencing page head
> on all page pointers, use page length arithmetic to only call page
> head when referencing a known different page head to avoid touching
> a cold cacheline.


Reviewed-by: Eric Dumazet <edumazet@...gle.com>