From: Igor Mammedov <imammedo@redhat.com>
Date: Thu, 13 Nov 2014 23:00:13 +0000 (+0000)
Subject: kvm: memslots: replace heap sort with an insertion sort pass
X-Git-Tag: omap-for-v3.19/fixes-rc1~43^2~62
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=063584d44377ebde5ebc6e99cedc1bc6561939d7;p=pandora-kernel.git

kvm: memslots: replace heap sort with an insertion sort pass

memslots is a sorted array.  When a slot is changed, heapsort (lib/sort.c)
would take O(n log n) time to update it; an optimized insertion sort will
only cost O(n) on an array with just one item out of order.

Replace sort() with a custom sort that takes advantage of memslots usage
pattern and the known position of the changed slot.

performance change of 128 memslots insertions with gradually increasing
size (the worst case):

      heap sort   custom sort
max:  249747      2500 cycles

with custom sort alg taking ~98% less then original
update time.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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