From: Mihai Caraman <mihai.caraman@freescale.com>
Date: Wed, 18 Jun 2014 07:15:22 +0000 (+0300)
Subject: KVM: PPC: e500mc: Enhance tlb invalidation condition on vcpu schedule
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~130^2~10^2~52
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1f0eeb7e1a88f46afa0f435cf7c34b0c84cf2394;p=pandora-kernel.git

KVM: PPC: e500mc: Enhance tlb invalidation condition on vcpu schedule

On vcpu schedule, the condition checked for tlb pollution is too loose.
The tlb entries of a vcpu become polluted (vs stale) only when a different
vcpu within the same logical partition runs in-between. Optimize the tlb
invalidation condition keeping last_vcpu per logical partition id.

With the new invalidation condition, a guest shows 4% performance improvement
on P5020DS while running a memory stress application with the cpu oversubscribed,
the other guest running a cpu intensive workload.

Guest - old invalidation condition
  real 3.89
  user 3.87
  sys 0.01

Guest - enhanced invalidation condition
  real 3.75
  user 3.73
  sys 0.01

Host
  real 3.70
  user 1.85
  sys 0.00

The memory stress application accesses 4KB pages backed by 75% of available
TLB0 entries:

char foo[ENTRIES][4096] __attribute__ ((aligned (4096)));

int main()
{
	char bar;
	int i, j;

	for (i = 0; i < ITERATIONS; i++)
        	for (j = 0; j < ENTRIES; j++)
            		bar = foo[j][0];

	return 0;
}

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Reviewed-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
---

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