Since kernel 3.12 (commit 34ff8dc08956098563989d8599840b130be81252 in
linux-stable.git in particular) the value for 'unlimited' in cgroup
memory limits changed from LLONG_MAX to ULLONG_MAX. Due to rather
unfortunate choice of our VIR_DOMAIN_MEMORY_PARAM_UNLIMITED constant
(which we transfer as an unsigned long long in Kibibytes), we ended up
with the situation described below (applies to x86_64):
- 2^64-1 (ULLONG_MAX) -- "unlimited" in kernel = 3.12
- 2^63-1 (LLONG_MAX) -- "unlimited" in kernel < 3.12
- 2^63-1024 -- our PARAM_UNLIMITED scaled to Bytes
- 2^53-1 -- our PARAM_UNLIMITED unscaled (in Kibibytes)
This means that when any number within (2^63-1, 2^64-1] is read from
memory cgroup, we are transferring that number instead of "unlimited".
Unfortunately, changing VIR_DOMAIN_MEMORY_PARAM_UNLIMITED would break
ABI compatibility and thus we have to resort to a different solution.
With this patch every value greater than PARAM_UNLIMITED means
"unlimited". Even though this may seem misleading, we are already in
such unclear situation when running 3.12 kernel with memory limits set
to 2^63.
One example showing most of the problems at once (with kernel 3.12.2):
# virsh memtune asdf --hard-limit 9007199254740991 --swap-hard-limit -1
# echo 12345678901234567890 >\
/sys/fs/cgroup/memory/machine/asdf.libvirt-qemu/memory.soft_limit_in_bytes
# virsh memtune asdf
hard_limit : 18014398509481983
soft_limit : 12056327051986884
swap_hard_limit: 18014398509481983
Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
---
src/util/vircgroup.c | 57 +++++++++++++++++++++++++++++++++++-----------------
1 file changed, 39 insertions(+), 18 deletions(-)
diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index 9674328..43eb649 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -1957,12 +1957,19 @@ int
virCgroupGetMemoryHardLimit(virCgroupPtr group, unsigned long long *kb)
{
long long unsigned int limit_in_bytes;
- int ret;
- ret = virCgroupGetValueU64(group,
- VIR_CGROUP_CONTROLLER_MEMORY,
- "memory.limit_in_bytes", &limit_in_bytes);
- if (ret == 0)
- *kb = limit_in_bytes >> 10;
+ int ret = -1;
+
+ if (virCgroupGetValueU64(group,
+ VIR_CGROUP_CONTROLLER_MEMORY,
+ "memory.limit_in_bytes", &limit_in_bytes) < 0)
+ goto cleanup;
+
+ *kb = limit_in_bytes >> 10;
+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+
+ ret = 0;
+ cleanup:
return ret;
}
@@ -2012,12 +2019,19 @@ int
virCgroupGetMemorySoftLimit(virCgroupPtr group, unsigned long long *kb)
{
long long unsigned int limit_in_bytes;
- int ret;
- ret = virCgroupGetValueU64(group,
- VIR_CGROUP_CONTROLLER_MEMORY,
- "memory.soft_limit_in_bytes", &limit_in_bytes);
- if (ret == 0)
- *kb = limit_in_bytes >> 10;
+ int ret = -1;
+
+ if (virCgroupGetValueU64(group,
+ VIR_CGROUP_CONTROLLER_MEMORY,
+ "memory.soft_limit_in_bytes", &limit_in_bytes) < 0)
+ goto cleanup;
+
+ *kb = limit_in_bytes >> 10;
+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+
+ ret = 0;
+ cleanup:
return ret;
}
@@ -2067,12 +2081,19 @@ int
virCgroupGetMemSwapHardLimit(virCgroupPtr group, unsigned long long *kb)
{
long long unsigned int limit_in_bytes;
- int ret;
- ret = virCgroupGetValueU64(group,
- VIR_CGROUP_CONTROLLER_MEMORY,
- "memory.memsw.limit_in_bytes", &limit_in_bytes);
- if (ret == 0)
- *kb = limit_in_bytes >> 10;
+ int ret = -1;
+
+ if (virCgroupGetValueU64(group,
+ VIR_CGROUP_CONTROLLER_MEMORY,
+ "memory.memsw.limit_in_bytes", &limit_in_bytes) < 0)
+ goto cleanup;
+
+ *kb = limit_in_bytes >> 10;
+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
+
+ ret = 0;
+ cleanup:
return ret;
}
--
1.8.4.4
--
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