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Re: [Xen-devel] [patch 6/6] netif_release_rx_bufs

To: Gerd Hoffmann <kraxel@xxxxxxx>, Xen devel list <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [patch 6/6] netif_release_rx_bufs
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 17 Aug 2006 16:04:51 +0100
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On 17/8/06 3:13 pm, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

> This patch adds a netif_release_rx_bufs() function to the netfront
> driver.  It intends to fix the rx buffer page leak.  Unfortunaly it
> doesn't work perfectly, the reason is that reclaiming the pages granted
> to the backend driver works only if the backend driver gave them back
> already, filled with network data.  Reclaiming unfilled rx buffers does
> NOT work.
> I think we need either a way to get back pages with transfer grants
> without cooperation from the backend driver, or we need some way to say
> "pretty pretty please, give me back my rx buffers" to the netback driver.

Unlike a map grant, you can reclaim a transfer grant at any time. The only
question is whether it has been used to transfer a page, or not.

 -- Keir

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