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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Eric Dumazet <edumazet@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Soheil Hassas Yeganeh <soheil@google.com>
Subject: Re: [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for zerocopy receive
Date: Wed, 25 Apr 2018 09:20:55 -0700	[thread overview]
Message-ID: <8ce78bd6-8142-2937-11fd-2e4a2b22d90c@gmail.com> (raw)
In-Reply-To: <20180425160413.GC8546@bombadil.infradead.org>



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.

  reply	other threads:[~2018-04-25 16:21 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25  5:27 [PATCH net-next 0/2] tcp: mmap: rework " Eric Dumazet
2018-04-25  5:27 ` [PATCH net-next 1/2] tcp: add TCP_ZEROCOPY_RECEIVE support for " Eric Dumazet
2018-04-25  6:28   ` Christoph Hellwig
2018-04-25 13:01     ` Eric Dumazet
2018-04-25 15:24       ` Christoph Hellwig
2018-04-25 16:04       ` Matthew Wilcox
2018-04-25 16:20         ` Eric Dumazet [this message]
2018-04-25 16:30           ` Matthew Wilcox
2018-04-25 16:22         ` Andy Lutomirski
2018-04-25 16:35           ` Eric Dumazet
2018-04-25 16:44             ` Eric Dumazet
2018-04-25 13:42   ` Eric Dumazet
2018-04-25  5:27 ` [PATCH net-next 2/2] selftests: net: tcp_mmap must use TCP_ZEROCOPY_RECEIVE Eric Dumazet

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