From 101420b886eec36990419bc9ed5b503622af8a0d Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Fri, 15 Jul 2016 12:03:50 +0200 Subject: [PATCH] exec: avoid realloc in phys_map_node_reserve this is the first step in reducing the brk heap fragmentation created by the map->nodes memory allocation. Since the introduction of RCU the freeing of the PhysPageMaps is delayed so that sometimes several hundred are allocated at the same time. Even worse the memory for map->nodes is allocated and shortly afterwards reallocated. Since the number of nodes it grows to in the end is the same for all PhysPageMaps remember this value and at least avoid the reallocation. The large number of simultaneous allocations (about 450 x 70kB in my configuration) has to be addressed later. Signed-off-by: Peter Lieven Message-Id: <1468577030-21097-1-git-send-email-pl@kamp.de> Signed-off-by: Paolo Bonzini --- exec.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/exec.c b/exec.c index 011babd584..60cf46a5b5 100644 --- a/exec.c +++ b/exec.c @@ -187,10 +187,12 @@ struct CPUAddressSpace { static void phys_map_node_reserve(PhysPageMap *map, unsigned nodes) { + static unsigned alloc_hint = 16; if (map->nodes_nb + nodes > map->nodes_nb_alloc) { - map->nodes_nb_alloc = MAX(map->nodes_nb_alloc * 2, 16); + map->nodes_nb_alloc = MAX(map->nodes_nb_alloc, alloc_hint); map->nodes_nb_alloc = MAX(map->nodes_nb_alloc, map->nodes_nb + nodes); map->nodes = g_renew(Node, map->nodes, map->nodes_nb_alloc); + alloc_hint = map->nodes_nb_alloc; } }