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Subject: Re: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for
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To:     Matthew Wilcox <willy@infradead.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Eric Dumazet <edumazet@google.com>,
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        linux-mm <linux-mm@kvack.org>,
        Soheil Hassas Yeganeh <soheil@google.com>
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From:   Eric Dumazet <eric.dumazet@gmail.com>
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Date:   Wed, 25 Apr 2018 09:20:55 -0700
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On 04/25/2018 09:04 AM, Matthew Wilcox wrote:

> If you don't zap the page range, any of the CPUs in the system where
> any thread in this task have ever run may have a TLB entry pointing to
> this page ... if the page is being recycled into the page allocator,
> then that page might end up as a slab page or page table or page cache
> while the other CPU still have access to it.

Yes, this makes sense.

> 
> You could hang onto the page until you've built up a sufficiently large
> batch, then bulk-invalidate all of the TLB entries, but we start to get
> into weirdnesses on different CPU architectures.
> 

zap_page_range() is already doing a bulk-invalidate,
so maybe vm_replace_page() wont bring serious improvement if we end-up doing same dance.

Thanks.