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Re: [Xen-devel] [RFC][PATCH] 1/3] [XEN] Use explicit bit sized fields for exported xentrace data.


  • To: George Dunlap <dunlapg@xxxxxxxxx>, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir@xxxxxxxxxxxxx>
  • Date: Thu, 30 Nov 2006 17:03:26 +0000
  • Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 30 Nov 2006 09:03:35 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AccUoXNMsgOsGoCUEdubHwAX8io7RQ==
  • Thread-topic: [Xen-devel] [RFC][PATCH] 1/3] [XEN] Use explicit bit sized fields for exported xentrace data.



On 30/11/06 16:58, "George Dunlap" <dunlapg@xxxxxxxxx> wrote:

> Hmm... this has the unfortunate side-effect of doubling the size of
> the trace, and effectively halving the effectiveness of the trace
> buffer in avoiding drops.  My moderate-length traces are already in
> the gigabyte range, and I occasionally lose trace records even with a
> buffer size of 256.  It would be really nice if we could avoid that.
> 
> I happen to be using the VMENTER/VMEXIT tracing, which could be
> consolidated into one record if we went to a 64-bit trace.  Is anyone
> else doing high-bandwidth tracing that this would affect in a
> significantly negative way?

As we move increasingly towards x86/64 this is an issue that will need to be
addressed even if we leave the tracing fields as longs.

 -- Keir


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