[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net-next] xen-netback: improve guest-receive-side flow control
> -----Original Message----- > From: David Vrabel > Sent: 02 December 2013 12:00 > To: Paul Durrant > Cc: xen-devel@xxxxxxxxxxxxx; Wei Liu; Ian Campbell > Subject: Re: [PATCH net-next] xen-netback: improve guest-receive-side flow > control > > On 02/12/13 11:55, Paul Durrant wrote: > >> -----Original Message----- > >> From: David Vrabel > >> Sent: 02 December 2013 11:52 > >> To: Paul Durrant > >> Cc: xen-devel@xxxxxxxxxxxxx; Wei Liu; Ian Campbell > >> Subject: Re: [PATCH net-next] xen-netback: improve guest-receive-side > flow > >> control > >> > >> On 28/11/13 13:11, Paul Durrant wrote: > >>> The flow control code relies on a double pass of tke skb, firstly to count > >>> the number of ring slots needed to supply sufficient grant references, > and > >>> another to actually consume those references and build the grant copy > >>> operations. It transpires that, in some scenarios, the initial count and > >>> the > >>> number of references consumed differs and, after this happens a > number > >> of > >>> times, flow control is completely broken. > >> > >> Can you describe in more detail the cases where it gets it wrong? > >> > > > > I've already elaborated on this thread (at Annie Li's request). That > > explanation is probably a little long for inclusion in the comment though. > > I understand that count_slot() going wrong is bad. What specifically is > it counting incorrectly. What frag layout is causing it? If this is > understood there may be a more more minimal patch we can mark for > stable. > TBH once I realised the value returned was different from xenvif_gop_skb() I didn' t look further; this function has needed putting out of its misery for a long time. Paul _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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