On Mon, Dec 09, 2013 at 09:22:51AM +0100, Martin Kletzander wrote:
> 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;
> }
ACK
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list