netdev - Re: [RFC 2/2] page_frag_cache: Store metadata in struct page

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Message-ID: <8e8c5cfa-ae76-e672-3da1-818b5df4448b@gmail.com>
Date:   Fri, 16 Mar 2018 14:32:22 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Alexander Duyck <alexander.duyck@...il.com>
Cc:     Alexander Duyck <alexander.h.duyck@...el.com>,
        linux-mm@...r.kernel.org, Netdev <netdev@...r.kernel.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>
Subject: Re: [RFC 2/2] page_frag_cache: Store metadata in struct page



On 03/16/2018 02:05 PM, Matthew Wilcox wrote:
  
> 
> Obviously if the problem turns out to be the cacheline thrashing rather
> than the call to page_to_virt, then this is pointless to test.
> 
>> I won't be able to test the patches until next week, but I expect I
>> will probably see a noticeable regression when performing a small
>> packet routing test.
> 
> I really appreciate you being willing to try this for me.  I need to
> get myself a dual-socket machine to test things like this.
>

It seems my prior mail/answer was lost.

Issue is cacheline thrashing indeed, particularly on PowerPC (64 KB pages)