Re: [XenPPC] PTEG full message

[Mark F Mergen <mergen@xxxxxxxxxx>]

Yes, such a message could be made informative,
at some debug level but not routinely, that pteg eviction code is being
activated.  However, there is a theoretical absolutely full state
when all ptes in a pteg and it's secondary hash twin are bolted, not just
valid or locked.  We definitely need a bug panic message in this case.
 Locked is a temporary state that prevents modification of a pte for
a short time, and it will go away in a short time.  A valid but not
locked or bolted entry can be made invalid and therefore evicted, so a
new pte can be entered in the pteg, even if there were no empty (invalid)
ptes when the pteg was first scanned.

Mark Mergen

Maria Butrico <butrico@xxxxxxxxxxxxx>
Sent by: xen-ppc-devel-bounces@xxxxxxxxxxxxxxxxxxx

07/14/2006 05:12 PM

Please respond to
butrico@xxxxxxxxxxxxxx

To
cc	xen-ppc-devel@xxxxxxxxxxxxxxxxxxx
Subject	Re: [XenPPC] PTEG full message

Maria Butrico wrote:
> As Dan and I were working on his blade, we got to a state where we
> thought that the system had hung.  We were seeing many many messages
> about the PTEG being full.  We removed the message, and after
a minute 
> delay the system started.  I think there maybe something wrong
there, 
> but we eventually made forward progress.  We did a bit of debugging
> before removing the message, and we did not see anything obviously
> wrong with the entry, so far.
>
> _______________________________________________
> Xen-ppc-devel mailing list
> Xen-ppc-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-ppc-devel
I did some more debugging on this, and when a pteg is declared full it
is indeed full and the pages there aren't at all that peculiar.  I
think 
we should remove the message entirely.   Also it is never the case
that 
the lock bit is on (for full pteg). 


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