From 0c1f21a28ec44f527237be9f810284de265c8522 Mon Sep 17 00:00:00 2001
From: Rafal Wojtczuk <rafal@invisiblethingslab.com>
Date: Fri, 10 Sep 2010 11:35:30 +0200
Subject: [PATCH] qmemman: when a AppVM is low on memory, allow small
 adjustments

A small AppVM (say, with 100MB total) can go below prefmem, and
still not be assigned memory, because of the MIN_TOTAL_MEMORY_TRANSFER
threshold.
So, if AppVM is below prefmem, allow for smaller mem-sets.
---
 common/meminfo-writer.c | 12 +++++++-----
 dom0/qmemman/qmemman.py |  8 +++++++-
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/common/meminfo-writer.c b/common/meminfo-writer.c
index d97c68df..2f6f2174 100644
--- a/common/meminfo-writer.c
+++ b/common/meminfo-writer.c
@@ -17,7 +17,8 @@ char *parse(char *buf)
 	static char outbuf[4096];
 	int val;
 	int len;
-	int MemTotal=0, MemFree=0, Buffers=0, Cached=0, SwapTotal=0, SwapFree=0;
+	int MemTotal = 0, MemFree = 0, Buffers = 0, Cached = 0, SwapTotal =
+	    0, SwapFree = 0;
 	unsigned long long key;
 	long used_mem, used_mem_diff;
 	int nitems = 0;
@@ -54,10 +55,12 @@ char *parse(char *buf)
 		return NULL;
 
 	used_mem_diff = used_mem - prev_used_mem;
-	prev_used_mem = used_mem;
 	if (used_mem_diff < 0)
 		used_mem_diff = -used_mem_diff;
-	if (used_mem_diff > used_mem_change_threshold) {
+	if (used_mem_diff > used_mem_change_threshold
+	    || (used_mem > prev_used_mem && used_mem * 13 / 10 > MemTotal
+		&& used_mem_diff > used_mem_change_threshold/2)) {
+		prev_used_mem = used_mem;
 		sprintf(outbuf,
 			"MemTotal: %d kB\nMemFree: %d kB\nBuffers: %d kB\nCached: %d kB\n"
 			"SwapTotal: %d kB\nSwapFree: %d kB\n", MemTotal,
@@ -82,8 +85,7 @@ void send_to_qmemman(struct xs_handle *xs, char *data)
 	}
 }
 
-int
-main(int argc, char **argv)
+int main(int argc, char **argv)
 {
 	char buf[4096];
 	int n;
diff --git a/dom0/qmemman/qmemman.py b/dom0/qmemman/qmemman.py
index eb9b4328..cbfc0543 100755
--- a/dom0/qmemman/qmemman.py
+++ b/dom0/qmemman/qmemman.py
@@ -101,10 +101,16 @@ class SystemState:
     def is_balance_req_significant(self, memset_reqs):
         total_memory_transfer = 0
         MIN_TOTAL_MEMORY_TRANSFER = 150*1024*1024
+        MIN_MEM_CHANGE_WHEN_UNDER_PREF = 15*1024*1024
         for rq in memset_reqs:
             dom, mem = rq
-            memory_change = mem - self.domdict[dom].last_target
+            last_target = self.domdict[dom].last_target
+            memory_change = mem - last_target
             total_memory_transfer += abs(memory_change)
+            pref = qmemman_algo.prefmem(self.domdict[dom])
+            if last_target > 0 and last_target < pref and memory_change > MIN_MEM_CHANGE_WHEN_UNDER_PREF:
+                print 'dom', dom, 'is below pref, allowing balance'
+                return True
         return total_memory_transfer > MIN_TOTAL_MEMORY_TRANSFER
 
     def print_stats(self, xenfree, memset_reqs):