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Make anon clustering more compatible.

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Make the clustering enabling knob more fine-grained by providing a
setting where the allocation with hint is not clustered. This is aimed
to be somewhat more compatible with e.g. go 1.4 which expects that
hinted mmap without MAP_FIXED does not change the allocation address.

Now the vm.cluster_anon can be set to 1 to only cluster when no hints,
and to 2 to always cluster.  Default value is 1.

Requested by: peter
Reviewed by:	emaste, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D19194
This commit is contained in:
Konstantin Belousov 2019-02-14 15:45:53 +00:00
parent 59621b207c
commit 484e9d0322
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=344128
1 changed files with 17 additions and 2 deletions
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19
sys/vm/vm_map.c
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@ -1487,7 +1487,22 @@ static const int aslr_pages_rnd_32[2] = {0x100, 0x4};
static int cluster_anon = 1;
SYSCTL_INT(_vm, OID_AUTO, cluster_anon, CTLFLAG_RW,
&cluster_anon, 0,
"Cluster anonymous mappings");
"Cluster anonymous mappings: 0 = no, 1 = yes if no hint, 2 = always");
static bool
clustering_anon_allowed(vm_offset_t addr)
{
switch (cluster_anon) {
case 0:
return (false);
case 1:
return (addr == 0);
case 2:
default:
return (true);
}
}
static long aslr_restarts;
SYSCTL_LONG(_vm, OID_AUTO, aslr_restarts, CTLFLAG_RD,
@ -1593,7 +1608,7 @@ vm_map_find(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
} else
alignment = 0;
en_aslr = (map->flags & MAP_ASLR) != 0;
update_anon = cluster = cluster_anon != 0 &&
update_anon = cluster = clustering_anon_allowed(*addr) &&
(map->flags & MAP_IS_SUB_MAP) == 0 && max_addr == 0 &&
find_space != VMFS_NO_SPACE && object == NULL &&
(cow & (MAP_INHERIT_SHARE | MAP_STACK_GROWS_UP |