linux-kernel - Re: 2.6.24-rc3, 4GB RAM, swiotlb, r8169, out of space

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Message-ID: <20071125011550.GB30759@electric-eye.fr.zoreil.com>
Date:	Sun, 25 Nov 2007 02:15:51 +0100
From:	Francois Romieu <romieu@...zoreil.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Alistair John Strachan <alistair@...zero.co.uk>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: 2.6.24-rc3, 4GB RAM, swiotlb, r8169, out of space

Alan Cox <alan@...rguk.ukuu.org.uk> :
[...]
> You seem to have a leak, which actually isn't suprising
> 
> 	rtl8169_xmit_frags allocates a set of maps for a fragmented packet
> 
> 	rtl8169_start_xmit allocates a buffer
> 
> When we finish the transit we free the main buffer (always using skb->len
> when sometimes its skb->headlne. We don't seem to free the fragment
> buffers at all.
> Looks like the unmap path for fragmented packets is broken with any kind
> of iommu

Are you referring to the pci_unmap part ?

There is a 1:1 correspondance between a Tx descriptor entry and
{an unfragmented skb or a fragment of a skb}. Afaiks rtl8169_unmap_tx_skb()
is issued for each Tx descriptor entry, be it after a Tx completion irq or
a general Tx ring cleanup.

I'll read it again after some sleep but the leak does not seem clear to me.

-- 
Ueimor
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