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From 47820a97323309465ebc3dd39a4dc74bd955a775 Mon Sep 17 00:00:00 2001
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Message-Id: <47820a97323309465ebc3dd39a4dc74bd955a775.1386932211.git.jdenemar@redhat.com>
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From: Martin Kletzander <mkletzan@redhat.com>
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Date: Tue, 10 Dec 2013 10:03:55 +0100
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Subject: [PATCH] cgroups: Redefine what "unlimited" means wrt memory limits
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https://bugzilla.redhat.com/show_bug.cgi?id=1024272
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Since kernel 3.12 (commit 34ff8dc08956098563989d8599840b130be81252 in
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linux-stable.git in particular) the value for 'unlimited' in cgroup
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memory limits changed from LLONG_MAX to ULLONG_MAX. Due to rather
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unfortunate choice of our VIR_DOMAIN_MEMORY_PARAM_UNLIMITED constant
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(which we transfer as an unsigned long long in Kibibytes), we ended up
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with the situation described below (applies to x86_64):
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- 2^64-1 (ULLONG_MAX) -- "unlimited" in kernel = 3.12
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- 2^63-1 (LLONG_MAX) -- "unlimited" in kernel < 3.12
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- 2^63-1024 -- our PARAM_UNLIMITED scaled to Bytes
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- 2^53-1 -- our PARAM_UNLIMITED unscaled (in Kibibytes)
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This means that when any number within (2^63-1, 2^64-1] is read from
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memory cgroup, we are transferring that number instead of "unlimited".
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Unfortunately, changing VIR_DOMAIN_MEMORY_PARAM_UNLIMITED would break
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ABI compatibility and thus we have to resort to a different solution.
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With this patch every value greater than PARAM_UNLIMITED means
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"unlimited". Even though this may seem misleading, we are already in
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such unclear situation when running 3.12 kernel with memory limits set
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to 2^63.
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One example showing most of the problems at once (with kernel 3.12.2):
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# virsh memtune asdf --hard-limit 9007199254740991 --swap-hard-limit -1
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# echo 12345678901234567890 >\
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/sys/fs/cgroup/memory/machine/asdf.libvirt-qemu/memory.soft_limit_in_bytes
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# virsh memtune asdf
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hard_limit : 18014398509481983
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soft_limit : 12056327051986884
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swap_hard_limit: 18014398509481983
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Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
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(cherry picked from commit 231656bbeb9e4d3bedc44362784c35eee21cf0f4)
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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src/util/vircgroup.c | 57 +++++++++++++++++++++++++++++++++++-----------------
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1 file changed, 39 insertions(+), 18 deletions(-)
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diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
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index cfb4b3f..ed53dff 100644
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--- a/src/util/vircgroup.c
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+++ b/src/util/vircgroup.c
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@@ -2069,12 +2069,19 @@ int virCgroupSetMemoryHardLimit(virCgroupPtr group, unsigned long long kb)
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int virCgroupGetMemoryHardLimit(virCgroupPtr group, unsigned long long *kb)
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{
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long long unsigned int limit_in_bytes;
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- int ret;
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- ret = virCgroupGetValueU64(group,
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- VIR_CGROUP_CONTROLLER_MEMORY,
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- "memory.limit_in_bytes", &limit_in_bytes);
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- if (ret == 0)
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- *kb = limit_in_bytes >> 10;
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+ int ret = -1;
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+
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+ if (virCgroupGetValueU64(group,
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+ VIR_CGROUP_CONTROLLER_MEMORY,
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+ "memory.limit_in_bytes", &limit_in_bytes) < 0)
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+ goto cleanup;
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+
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+ *kb = limit_in_bytes >> 10;
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+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
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+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
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+
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+ ret = 0;
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+ cleanup:
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return ret;
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}
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@@ -2121,12 +2128,19 @@ int virCgroupSetMemorySoftLimit(virCgroupPtr group, unsigned long long kb)
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int virCgroupGetMemorySoftLimit(virCgroupPtr group, unsigned long long *kb)
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{
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long long unsigned int limit_in_bytes;
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- int ret;
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- ret = virCgroupGetValueU64(group,
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- VIR_CGROUP_CONTROLLER_MEMORY,
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- "memory.soft_limit_in_bytes", &limit_in_bytes);
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- if (ret == 0)
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- *kb = limit_in_bytes >> 10;
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+ int ret = -1;
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+
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+ if (virCgroupGetValueU64(group,
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+ VIR_CGROUP_CONTROLLER_MEMORY,
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+ "memory.soft_limit_in_bytes", &limit_in_bytes) < 0)
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+ goto cleanup;
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+
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+ *kb = limit_in_bytes >> 10;
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+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
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+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
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+
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+ ret = 0;
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+ cleanup:
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return ret;
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}
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@@ -2172,12 +2186,19 @@ int virCgroupSetMemSwapHardLimit(virCgroupPtr group, unsigned long long kb)
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int virCgroupGetMemSwapHardLimit(virCgroupPtr group, unsigned long long *kb)
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{
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long long unsigned int limit_in_bytes;
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- int ret;
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- ret = virCgroupGetValueU64(group,
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- VIR_CGROUP_CONTROLLER_MEMORY,
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- "memory.memsw.limit_in_bytes", &limit_in_bytes);
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- if (ret == 0)
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- *kb = limit_in_bytes >> 10;
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+ int ret = -1;
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+
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+ if (virCgroupGetValueU64(group,
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+ VIR_CGROUP_CONTROLLER_MEMORY,
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+ "memory.memsw.limit_in_bytes", &limit_in_bytes) < 0)
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+ goto cleanup;
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+
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+ *kb = limit_in_bytes >> 10;
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+ if (*kb > VIR_DOMAIN_MEMORY_PARAM_UNLIMITED)
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+ *kb = VIR_DOMAIN_MEMORY_PARAM_UNLIMITED;
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+
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+ ret = 0;
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+ cleanup:
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return ret;
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}
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--
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1.8.5.1
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