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Re: [Xen-devel] [PATCH] tools: convert cpumap bitmap to list

To: Ryan Harper <ryanh@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] tools: convert cpumap bitmap to list
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 20 Oct 2005 11:44:06 +0100
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On 19 Oct 2005, at 23:45, Ryan Harper wrote:

This patch modifies the lowlevel xc vcpuinfo call to convert a vcpu's
cpumap to a list of int.  XendDomainInfo.py filters the cpumap into a
smaller list that is bound by the number of vcpus allocated to a domain.

Two things:

First, there is no correspondence between size of cpumap and max_vcpu_id, because there is no direct relationship between sizes of virtual and physical CPU spaces. We could have a system with more vcpus than physical cpus, or vice versa. And cpumap represents sets of physical cpus, not sets of virtual cpus.

Second, I meant that the cpumap list should contain just the list of physical cpus that that vcpu can run on. So, for example, a cpumap bitmask of 0x5 would correspond to the cpumap list [0, 2], not the list [0, -1, 2, -1, -1, ...]. The latter is a weird and redundant representation.

 -- Keir


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