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check memory limits for cgroupv1 #27

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check memory limits for cgroupv1 #27

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43 changes: 31 additions & 12 deletions src/unix/linux-core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,7 @@ static void read_speeds(unsigned int numcpus, uv_cpu_info_t* ci);
static uint64_t read_cpufreq(unsigned int cpunum);

int uv__platform_loop_init(uv_loop_t* loop) {

loop->inotify_fd = -1;
loop->inotify_watchers = NULL;

Expand Down Expand Up @@ -811,29 +811,48 @@ uint64_t uv_get_constrained_memory(void) {
uint64_t high;
uint64_t max;
char* p;
char* p_end;

if (uv__slurp("/proc/self/cgroup", buf, sizeof(buf)))
return uv__get_constrained_memory_fallback();

/* In the case of cgroupv2, we'll only have a single entry. */
if (memcmp(buf, "0::/", 4))
return uv__get_constrained_memory_fallback();
if (0 == memcmp(buf, "0::/", 4)) {
p = strchr(buf, '\n');
if (p != NULL)
*p = '\0';

p = buf + 4;

snprintf(filename, sizeof(filename), "/sys/fs/cgroup/%s/memory.max", p);
max = uv__read_uint64(filename);

snprintf(filename, sizeof(filename), "/sys/fs/cgroup/%s/memory.high", p);
high = uv__read_uint64(filename);
} else {
p = strchr(buf, ':');
while (p != NULL && memcmp(p, ":memory:", 8)) {
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@simonbyrne simonbyrne Oct 8, 2022

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oh wait, I realise this isn't how cgroups work...

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@simonbyrne simonbyrne Oct 8, 2022

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Actually, I think it is correct? But it would be good for someone who understands these things to check.

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@maleadt maleadt Oct 12, 2022

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I take it slurm creates a cgroup subtree? On my cgroupv1 system, the limit sits at /sys/fs/cgroup/memory directly. It'd be useful to add a comment here about what you're doing, that's easier to review than to parse C code 🙂

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@simonbyrne simonbyrne Oct 12, 2022

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Yes, that appears to be how cgroupv1 works, e.g. https://unix.stackexchange.com/a/621576

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@maleadt maleadt Oct 26, 2022

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Apparently we're still missing something though, as on my cgroup1 system with Docker, I can't access even the memory subgroup listed in /proc/self/cgroup.

p = strchr(p, '\n');
p = strchr(p, ':');
}
if (p == NULL)
return uv__get_constrained_memory_fallback();

p = strchr(buf, '\n');
if (p != NULL)
*p = '\0';
p = p + 8;
p_end = strchr(p, '\n');
if (p_end != NULL)
*p_end = '\0';

p = buf + 4;
snprintf(filename, sizeof(filename), "/sys/fs/cgroup/memory/%s/memory.limit_in_bytes", p);
max = uv__read_uint64(filename);

snprintf(filename, sizeof(filename), "/sys/fs/cgroup/%s/memory.max", p);
max = uv__read_uint64(filename);
snprintf(filename, sizeof(filename), "/sys/fs/cgroup/memory/%s/memory.soft_limit_in_bytes", p);
high = uv__read_uint64(filename);
}

if (max == 0)
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@maleadt maleadt Oct 12, 2022

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if (max == 0 || high == 0)

return uv__get_constrained_memory_fallback();

snprintf(filename, sizeof(filename), "/sys/fs/cgroup/%s/memory.high", p);
high = uv__read_uint64(filename);

if (high == 0)
return uv__get_constrained_memory_fallback();

Expand Down