[PATCH v2 0/1] MR10466: ntdll: Consider cgroup CPU limits in init_cpu_info().
On Linux, `init_cpu_info()` uses `sysconf(_SC_NPROCESSORS_ONLN)` which returns the host machine's total CPU count, ignoring cgroup CPU bandwidth limits. This causes applications that scale thread counts based on `GetSystemInfo().dwNumberOfProcessors` to over-subscribe CPUs in container environments (Docker, Kubernetes). This MR reads cgroup v2 `cpu.max` and cgroup v1 `cpu.cfs_quota_us`/`cpu.cfs_period_us` to determine the effective CPU limit, and clamps the reported processor count accordingly. For cgroup v2, it walks up the hierarchy to find the most restrictive quota. Falls back to `sysconf` when no cgroup limit is configured. GNU coreutils 9.8 (September 2025) added similar cgroup v2 awareness to `nproc`: https://github.com/coreutils/coreutils/issues/108 Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59556 ## Verification Verified with Wine built from this branch running inside Docker containers (cgroup v2). **Environment:** Docker on Linux (4-core host), Wine 11.4 with this patch applied. ### Without CPU limit ``` $ cat /sys/fs/cgroup/cpu.max max 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 4 ``` All 4 host CPUs are reported. No override is applied when `cpu.max` is unlimited. ### With `--cpus=1.4` ``` $ cat /sys/fs/cgroup/cpu.max 140000 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 1 ``` ### With `--cpus=1.5` ``` $ cat /sys/fs/cgroup/cpu.max 150000 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 2 ``` ### With `--cpus=2.0` ``` $ cat /sys/fs/cgroup/cpu.max 200000 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 2 ``` ### With `--cpus=2.4` ``` $ cat /sys/fs/cgroup/cpu.max 240000 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 2 ``` ### With `--cpus=2.5` ``` $ cat /sys/fs/cgroup/cpu.max 250000 100000 $ wine cmd /c "echo %NUMBER_OF_PROCESSORS%" 3 ``` The rounding uses `(double)quota / period + 0.5`, which rounds to the nearest integer. For example, `--cpus=1.4` rounds down to 1, while `--cpus=1.5` rounds up to 2. -- v2: ntdll: Consider cgroup CPU limits in init_cpu_info(). https://gitlab.winehq.org/wine/wine/-/merge_requests/10466
From: Hiroki Awata <castaneai@castaneai.net> On Linux, init_cpu_info() uses sysconf(_SC_NPROCESSORS_ONLN) which returns the host machine's total CPU count, ignoring cgroup CPU bandwidth limits. This causes applications that scale thread counts based on GetSystemInfo().dwNumberOfProcessors to over-subscribe CPUs in container environments (Docker, Kubernetes). Read cgroup v2 cpu.max and cgroup v1 cpu.cfs_quota_us/period_us to determine the effective CPU limit, and clamp the reported processor count accordingly. For cgroup v2, walk up the hierarchy to find the most restrictive quota. Fall back to sysconf when no cgroup limit is configured. Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59556 Signed-off-by: Hiroki Awata <castaneai@castaneai.net> --- dlls/ntdll/unix/system.c | 149 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) diff --git a/dlls/ntdll/unix/system.c b/dlls/ntdll/unix/system.c index aa66ec2654c..a864454159a 100644 --- a/dlls/ntdll/unix/system.c +++ b/dlls/ntdll/unix/system.c @@ -1623,6 +1623,145 @@ static void get_random( void *buf, ULONG len ) #endif } +#ifdef linux +static long read_cgroup_cpu_limit(void) +{ + char line[512], path[512], buf[1024], data[512]; + FILE *f; + long quota, period; + long result = 0; + char *s, *last_sep; + + /* Try cgroup v2 first: walk up the hierarchy for the lowest quota */ + f = fopen("/proc/self/cgroup", "r"); + if (f) + { + while (fgets(line, sizeof(line), f)) + { + if (!strncmp(line, "0::", 3)) + { + if ((s = strchr(line + 3, '\n'))) *s = 0; + snprintf(path, sizeof(path), "%s", line + 3); + fclose(f); + + while (*path) + { + snprintf(buf, sizeof(buf), "/sys/fs/cgroup%s/cpu.max", path); + f = fopen(buf, "r"); + if (f) + { + if (fgets(data, sizeof(data), f) && strncmp(data, "max", 3) != 0) + { + quota = strtol(data, &s, 10); + if (*s == ' ') + { + period = strtol(s + 1, NULL, 10); + if (period > 0) + { + long ncpus = (long)((double)quota / period + 0.5); + if (ncpus < 1) ncpus = 1; + if (!result || ncpus < result) result = ncpus; + } + } + } + fclose(f); + if (result == 1) return 1; + } + + last_sep = strrchr(path, '/'); + if (!last_sep) break; + if (last_sep == path && *(path + 1)) + *(path + 1) = 0; /* iterate on "/" too */ + else + *last_sep = 0; + } + + return result; + } + } + fclose(f); + } + + /* cgroup v1 fallback */ + f = fopen("/proc/self/cgroup", "r"); + if (!f) return 0; + + path[0] = 0; + while (fgets(line, sizeof(line), f)) + { + /* look for a line containing "cpu" controller, e.g. "4:cpu,cpuacct:/path" or "4:cpu:/path" */ + char *controllers, *cgroup_path; + s = strchr(line, ':'); + if (!s) continue; + controllers = s + 1; + s = strchr(controllers, ':'); + if (!s) continue; + *s = 0; + cgroup_path = s + 1; + if ((s = strchr(cgroup_path, '\n'))) *s = 0; + + /* check if "cpu" is one of the controllers */ + s = controllers; + while (*s) + { + char *end = s; + while (*end && *end != ',') end++; + if (end - s == 3 && !strncmp(s, "cpu", 3)) + { + snprintf(path, sizeof(path), "%s", cgroup_path); + break; + } + s = *end ? end + 1 : end; + } + if (path[0]) break; + } + fclose(f); + + if (!path[0]) return 0; + + /* try cpu,cpuacct mount point first, then cpu */ + snprintf(buf, sizeof(buf), "/sys/fs/cgroup/cpu,cpuacct%s/cpu.cfs_quota_us", path); + f = fopen(buf, "r"); + if (!f) + { + snprintf(buf, sizeof(buf), "/sys/fs/cgroup/cpu%s/cpu.cfs_quota_us", path); + f = fopen(buf, "r"); + } + if (!f) return 0; + + if (!fgets(buf, sizeof(buf), f)) + { + fclose(f); + return 0; + } + fclose(f); + quota = strtol(buf, NULL, 10); + if (quota <= 0) return 0; + + /* read period */ + snprintf(buf, sizeof(buf), "/sys/fs/cgroup/cpu,cpuacct%s/cpu.cfs_period_us", path); + f = fopen(buf, "r"); + if (!f) + { + snprintf(buf, sizeof(buf), "/sys/fs/cgroup/cpu%s/cpu.cfs_period_us", path); + f = fopen(buf, "r"); + } + if (!f) return 0; + + if (!fgets(buf, sizeof(buf), f)) + { + fclose(f); + return 0; + } + fclose(f); + period = strtol(buf, NULL, 10); + if (period <= 0) return 0; + + result = (long)((double)quota / period + 0.5); + return result < 1 ? 1 : result; +} +#endif + /****************************************************************** * init_cpu_info * @@ -1652,6 +1791,16 @@ void init_cpu_info(void) #else num = 1; FIXME("Detecting the number of processors is not supported.\n"); +#endif +#ifdef linux + { + long cgroup_cpus = read_cgroup_cpu_limit(); + if (cgroup_cpus > 0 && cgroup_cpus < num) + { + TRACE( "limiting to %ld CPUs from cgroup\n", cgroup_cpus ); + num = cgroup_cpus; + } + } #endif peb->NumberOfProcessors = num; init_cpu_model(); -- GitLab https://gitlab.winehq.org/wine/wine/-/merge_requests/10466
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Hiroki Awata -
Hiroki Awata (＠castaneai)