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Factorize cgroup memory access code

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This fixes the edge case that cgroup memory limit "0" is no longer
interpreted as "no limit" but as actual zero available memory, see (*).
The cgroup default setting "max" continues to be interpreted as "no
limit".

(*) https://docs.kernel.org/admin-guide/cgroup-v2.html
This commit is contained in:
Robert Schulze 2024-01-31 11:47:38 +00:00
parent 92a00d317c
commit ad0c0d8727
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GPG Key ID: 26703B55FB13728A
1 changed files with 29 additions and 22 deletions
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51
base/base/getMemoryAmount.cpp
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@ -13,6 +13,28 @@
#endif
namespace
{
std::optional<uint64_t> getCgroupsMemoryLimit(const std::string & setting)
{
#if defined(OS_LINUX)
std::filesystem::path default_cgroups_mount = "/sys/fs/cgroup";
std::ifstream file(default_cgroups_mount / setting);
if (!file.is_open())
return {};
uint64_t value;
if (file >> value)
return {value};
else
return {}; /// e.g. the cgroups default "max"
#else
return {};
#endif
}
}
/** Returns the size of physical memory (RAM) in bytes.
* Returns 0 on unsupported platform
*/
@ -28,35 +50,20 @@ uint64_t getMemoryAmountOrZero()
uint64_t memory_amount = num_pages * page_size;
#if defined(OS_LINUX)
/// Limit the memory amount by limits set by cgroups
std::filesystem::path default_cgroups_mount = "/sys/fs/cgroup";
/// Respect the memory limit set by cgroups
/// cgroups v2
std::ifstream cgroupv2_limit(default_cgroups_mount / "memory.max");
if (cgroupv2_limit.is_open())
{
uint64_t memory_limit = 0;
cgroupv2_limit >> memory_limit;
if (memory_limit > 0 && memory_limit < memory_amount)
memory_amount = memory_limit;
}
auto limit_v2 = getCgroupsMemoryLimit("memory.max");
if (limit_v2.has_value() && *limit_v2 < memory_amount)
memory_amount = *limit_v2;
else
{
/// cgroups v1
std::ifstream cgroup_limit(default_cgroups_mount / "memory/memory.limit_in_bytes");
if (cgroup_limit.is_open())
{
uint64_t memory_limit = 0; // in case of read error
cgroup_limit >> memory_limit;
if (memory_limit > 0 && memory_limit < memory_amount)
memory_amount = memory_limit;
}
auto limit_v1 = getCgroupsMemoryLimit("memory/memory.limit_in_bytes");
if (limit_v1.has_value() && *limit_v1 < memory_amount)
memory_amount = *limit_v1;
}
#endif
return memory_amount;
}