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[Xen-users] how to disable batching of page table entries updates for guest OS

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Qiang Zeng <zengqiang.buaa@xxxxxxxxx>
  • Date: Sun, 8 May 2011 22:27:28 -0400
  • Delivery-date: Sun, 08 May 2011 19:28:31 -0700
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Xen has a perf. enhancement by batching page table updates for the guest OS. I'm trying to measure the impact on the guest OS's performance, when this enhancement is disabled.

But I don't know how to disable it. I tried modifying do_mmu_update in xen/arch/x86/mm.c, which is to process the batch of page table updates requested by the guest OS. I simply limit it to only process one update:

<< for ( i = 0; i < count; i++ )

>> for ( i= 0; i < 1; i++)

However, after I install this version, there is a kernel panic.

An alternative may be to modify the code in the paravirtualized guest OS code, but I prefer to change xen code. Or do I HAVE to change the OS code rather than xen?

Could somebody provide some hints? Thanks!


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