tools/testing/selftests/cgroup/.gitignore | 1 + tools/testing/selftests/cgroup/Makefile | 2 + tools/testing/selftests/cgroup/config | 1 + tools/testing/selftests/cgroup/test_psi.c | 219 ++++++++++++++++++++++ 4 files changed, 223 insertions(+) create mode 100644 tools/testing/selftests/cgroup/test_psi.c
From: Tao Cui <cuitao@kylinos.cn>
The cgroup selftests have no PSI coverage. Add test_psi.c: per-resource
trigger smoke tests (one trigger per fd, IRQ full-only), a
cgroup.pressure hide/show toggle test, and two CPU-pressure trigger
tests using over-subscription: one expects the trigger to fire at a
tiny threshold, the other expects it not to fire at a whole-window
threshold. Skips when PSI is disabled or a resource is absent.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
Changes since v5 (Michal Koutny review):
- Terminate trigger writes with a newline instead of a NUL. The parser
(psi_write()) overwrites the last byte of the write with a NUL, so a
plain strlen()-sized write silently truncates the last digit for
privileged users (e.g. a 2000000us window becomes 200000us) and
fails with EINVAL for unprivileged ones. The newline keeps the
payload intact and drops the reliance on the undocumented NUL
convention.
- Keep pressure_open() silent: the SKIP message already reports why a
resource is unavailable and strace accompanies these tests anyway.
This replaces the ksft_perror() added on review of v4, which
duplicated the SKIP reason.
- Treat a test cgroup creation failure in FIXTURE_SETUP() as a failure
instead of a SKIP.
- Drop the unprivileged-minimum remark from the fire test comment and
the duplicate sysconf() error report.
- Add cgroup_trigger_no_fire, the false-trigger side of the firing
test: with the threshold equal to the whole window, ncpus+1 hogs must
not fire it. Under this oversubscription the measured cpu.pressure
"some" stays in the 2-17% range on 2- and 16-CPU machines, so the
margin is comfortable.
Changes since v4 (Suren Baghdasaryan review):
- Report pressure_open() errors with ksft_perror() instead of a raw
fprintf.
- Create the test cgroup in FIXTURE_SETUP() so that setup and teardown
are symmetric, and drop the per-test creation and the NULL guard in
the teardown.
- Factor the identical bodies of proc_trigger_io/memory/cpu into
test_psi_write(); the helper takes _metadata so that its ASSERTs
attribute to the calling test, following the seccomp selftests
precedent.
- Drop the now-unneeded NULL init of self->cg and the stale stdbool.h
include left over from the restructuring.
Changes since v3 (Suren Baghdasaryan review):
- Convert to the kselftest harness: each case is a TEST_F(psi, ...)
with the cgroup root/PSI availability checks in FIXTURE_SETUP() and
the teardown (kill hogs, destroy cgroup) in FIXTURE_TEARDOWN(),
which also removes the "ret"/"created" bookkeeping.
- A trigger that does not fire within the poll timeout is now a FAIL
instead of a SKIP: ncpus+1 hogs with a 1usec threshold must stall,
so a timeout indicates a real problem.
- Treat a poll() timeout and a poll() error uniformly via ASSERT.
- Check sysconf(_SC_NPROCESSORS_ONLN) only for -1 and report
strerror(errno); declare variables one per line; for(;;) {}.
- Make hog_cpu() die with the runner via PR_SET_PDEATHSIG so an
interrupted run does not leave orphaned hogs pinning every CPU.
Changes since v2 (Suren Baghdasaryan, Michal Koutny review):
- Restructure the trigger test into per-resource cases (io, memory, cpu,
irq) so a failure points at the specific resource; irq is skipped when
/proc/pressure/irq is absent.
- Spawn the CPU hogs with cg_run_nowait() instead of open-coding fork(),
and arm the trigger with a 2s window so unprivileged users can set it.
- Address the remaining review comments on cleanup and robustness:
guard teardown with a "created" flag, use cg_read_strcmp() instead of
atoi(), report strerror() on errors, and fix the unused-parameter and
sign-compare nits.
Changes since v1 (Michal Koutny, sashiko review):
- Keep trigger tests smoke-level; switch the firing test from memory to
CPU pressure; drop churn_memory().
- Keep the runner out of the cgroup; add PSI/IRQ skip-guards and a
.gitignore entry.
v1: https://lore.kernel.org/all/20260724025826.504586-1-cui.tao@linux.dev/
v2: https://lore.kernel.org/all/20260728083742.2359320-1-cui.tao@linux.dev/
v3: https://lore.kernel.org/all/20260813133723.1663605-1-cui.tao@linux.dev/
v4: https://lore.kernel.org/all/20260824085913.546741-1-cui.tao@linux.dev/
v5: https://lore.kernel.org/all/20260902040725.877155-1-cui.tao@linux.dev/
---
tools/testing/selftests/cgroup/.gitignore | 1 +
tools/testing/selftests/cgroup/Makefile | 2 +
tools/testing/selftests/cgroup/config | 1 +
tools/testing/selftests/cgroup/test_psi.c | 219 ++++++++++++++++++++++
4 files changed, 223 insertions(+)
create mode 100644 tools/testing/selftests/cgroup/test_psi.c
diff --git a/tools/testing/selftests/cgroup/.gitignore b/tools/testing/selftests/cgroup/.gitignore
index 952e4448bf070..ce2b907c57ea3 100644
--- a/tools/testing/selftests/cgroup/.gitignore
+++ b/tools/testing/selftests/cgroup/.gitignore
@@ -8,5 +8,6 @@ test_kill
test_kmem
test_memcontrol
test_pids
+test_psi
test_zswap
wait_inotify
diff --git a/tools/testing/selftests/cgroup/Makefile b/tools/testing/selftests/cgroup/Makefile
index e01584c2189ac..a8c69e37332a4 100644
--- a/tools/testing/selftests/cgroup/Makefile
+++ b/tools/testing/selftests/cgroup/Makefile
@@ -16,6 +16,7 @@ TEST_GEN_PROGS += test_kill
TEST_GEN_PROGS += test_kmem
TEST_GEN_PROGS += test_memcontrol
TEST_GEN_PROGS += test_pids
+TEST_GEN_PROGS += test_psi
TEST_GEN_PROGS += test_zswap
LOCAL_HDRS += $(selfdir)/clone3/clone3_selftests.h $(selfdir)/pidfd/pidfd.h
@@ -32,4 +33,5 @@ $(OUTPUT)/test_kill: $(LIBCGROUP_O)
$(OUTPUT)/test_kmem: $(LIBCGROUP_O)
$(OUTPUT)/test_memcontrol: $(LIBCGROUP_O)
$(OUTPUT)/test_pids: $(LIBCGROUP_O)
+$(OUTPUT)/test_psi: $(LIBCGROUP_O)
$(OUTPUT)/test_zswap: $(LIBCGROUP_O)
diff --git a/tools/testing/selftests/cgroup/config b/tools/testing/selftests/cgroup/config
index 39f979690dd3b..8a3ef479e83d3 100644
--- a/tools/testing/selftests/cgroup/config
+++ b/tools/testing/selftests/cgroup/config
@@ -4,3 +4,4 @@ CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_SCHED=y
CONFIG_MEMCG=y
CONFIG_PAGE_COUNTER=y
+CONFIG_PSI=y
diff --git a/tools/testing/selftests/cgroup/test_psi.c b/tools/testing/selftests/cgroup/test_psi.c
new file mode 100644
index 0000000000000..95dcb8a9f1843
--- /dev/null
+++ b/tools/testing/selftests/cgroup/test_psi.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/prctl.h>
+#include <linux/limits.h>
+
+#include "../kselftest_harness.h"
+#include "cgroup_util.h"
+
+#define PSI_POLL_TIMEOUT_MS 5000
+
+/*
+ * The kernel parser overwrites the last byte of a trigger write with a
+ * NUL, so terminate with a newline to keep the payload intact.
+ */
+static ssize_t write_trigger(int fd, const char *trigger)
+{
+ char buf[64];
+
+ snprintf(buf, sizeof(buf), "%s\n", trigger);
+
+ return write(fd, buf, strlen(buf));
+}
+
+static int pressure_open(const char *resource)
+{
+ char path[PATH_MAX];
+
+ snprintf(path, sizeof(path), "/proc/pressure/%s", resource);
+ return open(path, O_RDWR);
+}
+
+FIXTURE(psi)
+{
+ char root[PATH_MAX];
+ char *cg;
+};
+
+FIXTURE_SETUP(psi)
+{
+ int psi_fd;
+
+ if (cg_find_unified_root(self->root, sizeof(self->root), NULL))
+ SKIP(return, "cgroup v2 isn't mounted");
+
+ /* PSI must be enabled (CONFIG_PSI=y, not disabled on the cmdline). */
+ psi_fd = open("/proc/pressure/memory", O_RDONLY);
+ if (psi_fd < 0)
+ SKIP(return, "PSI unavailable (CONFIG_PSI=n or psi=0)");
+ close(psi_fd);
+
+ self->cg = cg_name(self->root, "psi_trigger_test");
+ ASSERT_NE(NULL, self->cg);
+ ASSERT_EQ(0, cg_create(self->cg));
+}
+
+FIXTURE_TEARDOWN(psi)
+{
+ cg_killall(self->cg);
+ cg_destroy(self->cg);
+ free(self->cg);
+}
+
+/*
+ * /proc/pressure/<resource> accepts exactly one trigger per file
+ * descriptor. Verify that a "some" trigger arms and that a second
+ * trigger on the same fd is rejected with EBUSY.
+ */
+static void test_psi_write(struct __test_metadata *_metadata,
+ const char *filename)
+{
+ int fd;
+
+ fd = pressure_open(filename);
+ ASSERT_GE(fd, 0);
+ ASSERT_GT(write_trigger(fd, "some 150000 2000000"), 0);
+ ASSERT_EQ(-1, write_trigger(fd, "full 150000 2000000"));
+ ASSERT_EQ(EBUSY, errno);
+ close(fd);
+}
+
+TEST_F(psi, proc_trigger_io)
+{
+ test_psi_write(_metadata, "io");
+}
+
+TEST_F(psi, proc_trigger_memory)
+{
+ test_psi_write(_metadata, "memory");
+}
+
+TEST_F(psi, proc_trigger_cpu)
+{
+ test_psi_write(_metadata, "cpu");
+}
+
+/*
+ * irq only tracks "full", so a "some" trigger must be rejected while a
+ * "full" trigger arms. irq is optional -- it only exists with IRQ-time
+ * accounting -- so a missing /proc/pressure/irq is SKIP, not FAIL.
+ */
+TEST_F(psi, proc_trigger_irq)
+{
+ int fd;
+
+ fd = pressure_open("irq");
+ if (fd < 0)
+ SKIP(return, "/proc/pressure/irq unavailable");
+
+ ASSERT_EQ(-1, write_trigger(fd, "some 150000 2000000"));
+ ASSERT_GT(write_trigger(fd, "full 150000 2000000"), 0);
+ close(fd);
+}
+
+/*
+ * cgroup.pressure gates visibility of the per-resource *.pressure files
+ * inside a cgroup: writing 0 hides them, writing 1 shows them again.
+ * Drive one hide/show cycle and check that memory.pressure appears and
+ * disappears along with it.
+ */
+TEST_F(psi, cgroup_pressure_toggle)
+{
+ char buf[BUF_SIZE];
+
+ ASSERT_EQ(0, cg_write(self->cg, "cgroup.pressure", "0"));
+ ASSERT_EQ(0, cg_read_strcmp(self->cg, "cgroup.pressure", "0\n"));
+ ASSERT_LT(cg_read(self->cg, "memory.pressure", buf, sizeof(buf)), 0);
+
+ ASSERT_EQ(0, cg_write(self->cg, "cgroup.pressure", "1"));
+ ASSERT_EQ(0, cg_read_strcmp(self->cg, "cgroup.pressure", "1\n"));
+ ASSERT_GE(cg_read(self->cg, "memory.pressure", buf, sizeof(buf)), 0);
+}
+
+/*
+ * A child that burns CPU forever; stopped by cg_killall() on teardown.
+ * It also dies with the runner, so an interrupted run (e.g. Ctrl-C
+ * during poll()) does not leave orphaned hogs pinning every CPU.
+ */
+static int hog_cpu(const char *cgroup, void *arg)
+{
+ prctl(PR_SET_PDEATHSIG, SIGKILL);
+ for (;;) {}
+ return 0;
+}
+
+/*
+ * Arm a "some" trigger on a cgroup's cpu.pressure, oversubscribe the
+ * cgroup with more spinning hogs than there are CPUs, and check that the
+ * trigger fires once the cgroup stalls on CPU.
+ */
+TEST_F(psi, cgroup_trigger_fire)
+{
+ char *cpupress;
+ struct pollfd pfd = { .events = POLLPRI };
+ long ncpus;
+ int fd;
+ int i;
+
+ cpupress = cg_control(self->cg, "cpu.pressure");
+ ASSERT_NE(NULL, cpupress);
+ fd = open(cpupress, O_RDWR);
+ free(cpupress);
+ ASSERT_GE(fd, 0);
+ pfd.fd = fd;
+
+ /* 1usec threshold over a 2s window: any CPU stall fires it. */
+ ASSERT_GT(write_trigger(fd, "some 1 2000000"), 0);
+
+ ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+ ASSERT_NE(-1, ncpus);
+
+ /* ncpus+1 hogs guarantee CPU contention inside the cgroup. */
+ for (i = 0; i < ncpus + 1; i++)
+ ASSERT_GE(cg_run_nowait(self->cg, hog_cpu, NULL), 0);
+
+ ASSERT_EQ(1, poll(&pfd, 1, PSI_POLL_TIMEOUT_MS));
+ ASSERT_NE(0, pfd.revents & POLLPRI);
+ close(fd);
+}
+
+/*
+ * The flip side of cgroup_trigger_fire: with the threshold equal to the
+ * whole window, even ncpus+1 hogs must not accumulate enough stall to
+ * fire the trigger.
+ */
+TEST_F(psi, cgroup_trigger_no_fire)
+{
+ char *cpupress;
+ struct pollfd pfd = { .events = POLLPRI };
+ long ncpus;
+ int fd;
+ int i;
+
+ cpupress = cg_control(self->cg, "cpu.pressure");
+ ASSERT_NE(NULL, cpupress);
+ fd = open(cpupress, O_RDWR);
+ free(cpupress);
+ ASSERT_GE(fd, 0);
+ pfd.fd = fd;
+
+ ASSERT_GT(write_trigger(fd, "some 2000000 2000000"), 0);
+
+ ncpus = sysconf(_SC_NPROCESSORS_ONLN);
+ ASSERT_NE(-1, ncpus);
+
+ for (i = 0; i < ncpus + 1; i++)
+ ASSERT_GE(cg_run_nowait(self->cg, hog_cpu, NULL), 0);
+
+ ASSERT_EQ(0, poll(&pfd, 1, PSI_POLL_TIMEOUT_MS));
+ close(fd);
+}
+
+TEST_HARNESS_MAIN
--
2.43.0On Thu, Sep 3, 2026 at 12:35 AM Tao Cui <cui.tao@linux.dev> wrote:
>
> From: Tao Cui <cuitao@kylinos.cn>
>
> The cgroup selftests have no PSI coverage. Add test_psi.c: per-resource
> trigger smoke tests (one trigger per fd, IRQ full-only), a
> cgroup.pressure hide/show toggle test, and two CPU-pressure trigger
> tests using over-subscription: one expects the trigger to fire at a
> tiny threshold, the other expects it not to fire at a whole-window
> threshold. Skips when PSI is disabled or a resource is absent.
>
> Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Thanks!
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
>
> ---
> Changes since v5 (Michal Koutny review):
> - Terminate trigger writes with a newline instead of a NUL. The parser
> (psi_write()) overwrites the last byte of the write with a NUL, so a
> plain strlen()-sized write silently truncates the last digit for
> privileged users (e.g. a 2000000us window becomes 200000us) and
> fails with EINVAL for unprivileged ones. The newline keeps the
> payload intact and drops the reliance on the undocumented NUL
> convention.
> - Keep pressure_open() silent: the SKIP message already reports why a
> resource is unavailable and strace accompanies these tests anyway.
> This replaces the ksft_perror() added on review of v4, which
> duplicated the SKIP reason.
> - Treat a test cgroup creation failure in FIXTURE_SETUP() as a failure
> instead of a SKIP.
> - Drop the unprivileged-minimum remark from the fire test comment and
> the duplicate sysconf() error report.
> - Add cgroup_trigger_no_fire, the false-trigger side of the firing
> test: with the threshold equal to the whole window, ncpus+1 hogs must
> not fire it. Under this oversubscription the measured cpu.pressure
> "some" stays in the 2-17% range on 2- and 16-CPU machines, so the
> margin is comfortable.
>
> Changes since v4 (Suren Baghdasaryan review):
> - Report pressure_open() errors with ksft_perror() instead of a raw
> fprintf.
> - Create the test cgroup in FIXTURE_SETUP() so that setup and teardown
> are symmetric, and drop the per-test creation and the NULL guard in
> the teardown.
> - Factor the identical bodies of proc_trigger_io/memory/cpu into
> test_psi_write(); the helper takes _metadata so that its ASSERTs
> attribute to the calling test, following the seccomp selftests
> precedent.
> - Drop the now-unneeded NULL init of self->cg and the stale stdbool.h
> include left over from the restructuring.
>
> Changes since v3 (Suren Baghdasaryan review):
> - Convert to the kselftest harness: each case is a TEST_F(psi, ...)
> with the cgroup root/PSI availability checks in FIXTURE_SETUP() and
> the teardown (kill hogs, destroy cgroup) in FIXTURE_TEARDOWN(),
> which also removes the "ret"/"created" bookkeeping.
> - A trigger that does not fire within the poll timeout is now a FAIL
> instead of a SKIP: ncpus+1 hogs with a 1usec threshold must stall,
> so a timeout indicates a real problem.
> - Treat a poll() timeout and a poll() error uniformly via ASSERT.
> - Check sysconf(_SC_NPROCESSORS_ONLN) only for -1 and report
> strerror(errno); declare variables one per line; for(;;) {}.
> - Make hog_cpu() die with the runner via PR_SET_PDEATHSIG so an
> interrupted run does not leave orphaned hogs pinning every CPU.
>
> Changes since v2 (Suren Baghdasaryan, Michal Koutny review):
> - Restructure the trigger test into per-resource cases (io, memory, cpu,
> irq) so a failure points at the specific resource; irq is skipped when
> /proc/pressure/irq is absent.
> - Spawn the CPU hogs with cg_run_nowait() instead of open-coding fork(),
> and arm the trigger with a 2s window so unprivileged users can set it.
> - Address the remaining review comments on cleanup and robustness:
> guard teardown with a "created" flag, use cg_read_strcmp() instead of
> atoi(), report strerror() on errors, and fix the unused-parameter and
> sign-compare nits.
>
> Changes since v1 (Michal Koutny, sashiko review):
> - Keep trigger tests smoke-level; switch the firing test from memory to
> CPU pressure; drop churn_memory().
> - Keep the runner out of the cgroup; add PSI/IRQ skip-guards and a
> .gitignore entry.
>
> v1: https://lore.kernel.org/all/20260724025826.504586-1-cui.tao@linux.dev/
> v2: https://lore.kernel.org/all/20260728083742.2359320-1-cui.tao@linux.dev/
> v3: https://lore.kernel.org/all/20260813133723.1663605-1-cui.tao@linux.dev/
> v4: https://lore.kernel.org/all/20260824085913.546741-1-cui.tao@linux.dev/
> v5: https://lore.kernel.org/all/20260902040725.877155-1-cui.tao@linux.dev/
> ---
> tools/testing/selftests/cgroup/.gitignore | 1 +
> tools/testing/selftests/cgroup/Makefile | 2 +
> tools/testing/selftests/cgroup/config | 1 +
> tools/testing/selftests/cgroup/test_psi.c | 219 ++++++++++++++++++++++
> 4 files changed, 223 insertions(+)
> create mode 100644 tools/testing/selftests/cgroup/test_psi.c
>
> diff --git a/tools/testing/selftests/cgroup/.gitignore b/tools/testing/selftests/cgroup/.gitignore
> index 952e4448bf070..ce2b907c57ea3 100644
> --- a/tools/testing/selftests/cgroup/.gitignore
> +++ b/tools/testing/selftests/cgroup/.gitignore
> @@ -8,5 +8,6 @@ test_kill
> test_kmem
> test_memcontrol
> test_pids
> +test_psi
> test_zswap
> wait_inotify
> diff --git a/tools/testing/selftests/cgroup/Makefile b/tools/testing/selftests/cgroup/Makefile
> index e01584c2189ac..a8c69e37332a4 100644
> --- a/tools/testing/selftests/cgroup/Makefile
> +++ b/tools/testing/selftests/cgroup/Makefile
> @@ -16,6 +16,7 @@ TEST_GEN_PROGS += test_kill
> TEST_GEN_PROGS += test_kmem
> TEST_GEN_PROGS += test_memcontrol
> TEST_GEN_PROGS += test_pids
> +TEST_GEN_PROGS += test_psi
> TEST_GEN_PROGS += test_zswap
>
> LOCAL_HDRS += $(selfdir)/clone3/clone3_selftests.h $(selfdir)/pidfd/pidfd.h
> @@ -32,4 +33,5 @@ $(OUTPUT)/test_kill: $(LIBCGROUP_O)
> $(OUTPUT)/test_kmem: $(LIBCGROUP_O)
> $(OUTPUT)/test_memcontrol: $(LIBCGROUP_O)
> $(OUTPUT)/test_pids: $(LIBCGROUP_O)
> +$(OUTPUT)/test_psi: $(LIBCGROUP_O)
> $(OUTPUT)/test_zswap: $(LIBCGROUP_O)
> diff --git a/tools/testing/selftests/cgroup/config b/tools/testing/selftests/cgroup/config
> index 39f979690dd3b..8a3ef479e83d3 100644
> --- a/tools/testing/selftests/cgroup/config
> +++ b/tools/testing/selftests/cgroup/config
> @@ -4,3 +4,4 @@ CONFIG_CGROUP_FREEZER=y
> CONFIG_CGROUP_SCHED=y
> CONFIG_MEMCG=y
> CONFIG_PAGE_COUNTER=y
> +CONFIG_PSI=y
> diff --git a/tools/testing/selftests/cgroup/test_psi.c b/tools/testing/selftests/cgroup/test_psi.c
> new file mode 100644
> index 0000000000000..95dcb8a9f1843
> --- /dev/null
> +++ b/tools/testing/selftests/cgroup/test_psi.c
> @@ -0,0 +1,219 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <poll.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/prctl.h>
> +#include <linux/limits.h>
> +
> +#include "../kselftest_harness.h"
> +#include "cgroup_util.h"
> +
> +#define PSI_POLL_TIMEOUT_MS 5000
> +
> +/*
> + * The kernel parser overwrites the last byte of a trigger write with a
> + * NUL, so terminate with a newline to keep the payload intact.
> + */
> +static ssize_t write_trigger(int fd, const char *trigger)
> +{
> + char buf[64];
> +
> + snprintf(buf, sizeof(buf), "%s\n", trigger);
> +
> + return write(fd, buf, strlen(buf));
> +}
> +
> +static int pressure_open(const char *resource)
> +{
> + char path[PATH_MAX];
> +
> + snprintf(path, sizeof(path), "/proc/pressure/%s", resource);
> + return open(path, O_RDWR);
> +}
> +
> +FIXTURE(psi)
> +{
> + char root[PATH_MAX];
> + char *cg;
> +};
> +
> +FIXTURE_SETUP(psi)
> +{
> + int psi_fd;
> +
> + if (cg_find_unified_root(self->root, sizeof(self->root), NULL))
> + SKIP(return, "cgroup v2 isn't mounted");
> +
> + /* PSI must be enabled (CONFIG_PSI=y, not disabled on the cmdline). */
> + psi_fd = open("/proc/pressure/memory", O_RDONLY);
> + if (psi_fd < 0)
> + SKIP(return, "PSI unavailable (CONFIG_PSI=n or psi=0)");
> + close(psi_fd);
> +
> + self->cg = cg_name(self->root, "psi_trigger_test");
> + ASSERT_NE(NULL, self->cg);
> + ASSERT_EQ(0, cg_create(self->cg));
> +}
> +
> +FIXTURE_TEARDOWN(psi)
> +{
> + cg_killall(self->cg);
> + cg_destroy(self->cg);
> + free(self->cg);
> +}
> +
> +/*
> + * /proc/pressure/<resource> accepts exactly one trigger per file
> + * descriptor. Verify that a "some" trigger arms and that a second
> + * trigger on the same fd is rejected with EBUSY.
> + */
> +static void test_psi_write(struct __test_metadata *_metadata,
> + const char *filename)
> +{
> + int fd;
> +
> + fd = pressure_open(filename);
> + ASSERT_GE(fd, 0);
> + ASSERT_GT(write_trigger(fd, "some 150000 2000000"), 0);
> + ASSERT_EQ(-1, write_trigger(fd, "full 150000 2000000"));
> + ASSERT_EQ(EBUSY, errno);
> + close(fd);
> +}
> +
> +TEST_F(psi, proc_trigger_io)
> +{
> + test_psi_write(_metadata, "io");
> +}
> +
> +TEST_F(psi, proc_trigger_memory)
> +{
> + test_psi_write(_metadata, "memory");
> +}
> +
> +TEST_F(psi, proc_trigger_cpu)
> +{
> + test_psi_write(_metadata, "cpu");
> +}
> +
> +/*
> + * irq only tracks "full", so a "some" trigger must be rejected while a
> + * "full" trigger arms. irq is optional -- it only exists with IRQ-time
> + * accounting -- so a missing /proc/pressure/irq is SKIP, not FAIL.
> + */
> +TEST_F(psi, proc_trigger_irq)
> +{
> + int fd;
> +
> + fd = pressure_open("irq");
> + if (fd < 0)
> + SKIP(return, "/proc/pressure/irq unavailable");
> +
> + ASSERT_EQ(-1, write_trigger(fd, "some 150000 2000000"));
> + ASSERT_GT(write_trigger(fd, "full 150000 2000000"), 0);
> + close(fd);
> +}
> +
> +/*
> + * cgroup.pressure gates visibility of the per-resource *.pressure files
> + * inside a cgroup: writing 0 hides them, writing 1 shows them again.
> + * Drive one hide/show cycle and check that memory.pressure appears and
> + * disappears along with it.
> + */
> +TEST_F(psi, cgroup_pressure_toggle)
> +{
> + char buf[BUF_SIZE];
> +
> + ASSERT_EQ(0, cg_write(self->cg, "cgroup.pressure", "0"));
> + ASSERT_EQ(0, cg_read_strcmp(self->cg, "cgroup.pressure", "0\n"));
> + ASSERT_LT(cg_read(self->cg, "memory.pressure", buf, sizeof(buf)), 0);
> +
> + ASSERT_EQ(0, cg_write(self->cg, "cgroup.pressure", "1"));
> + ASSERT_EQ(0, cg_read_strcmp(self->cg, "cgroup.pressure", "1\n"));
> + ASSERT_GE(cg_read(self->cg, "memory.pressure", buf, sizeof(buf)), 0);
> +}
> +
> +/*
> + * A child that burns CPU forever; stopped by cg_killall() on teardown.
> + * It also dies with the runner, so an interrupted run (e.g. Ctrl-C
> + * during poll()) does not leave orphaned hogs pinning every CPU.
Did you mean to say "orphaned hogs spinning on every CPU"?
> + */
> +static int hog_cpu(const char *cgroup, void *arg)
> +{
> + prctl(PR_SET_PDEATHSIG, SIGKILL);
> + for (;;) {}
> + return 0;
> +}
> +
> +/*
> + * Arm a "some" trigger on a cgroup's cpu.pressure, oversubscribe the
> + * cgroup with more spinning hogs than there are CPUs, and check that the
> + * trigger fires once the cgroup stalls on CPU.
> + */
> +TEST_F(psi, cgroup_trigger_fire)
> +{
> + char *cpupress;
> + struct pollfd pfd = { .events = POLLPRI };
> + long ncpus;
> + int fd;
> + int i;
> +
> + cpupress = cg_control(self->cg, "cpu.pressure");
> + ASSERT_NE(NULL, cpupress);
> + fd = open(cpupress, O_RDWR);
> + free(cpupress);
> + ASSERT_GE(fd, 0);
> + pfd.fd = fd;
> +
> + /* 1usec threshold over a 2s window: any CPU stall fires it. */
> + ASSERT_GT(write_trigger(fd, "some 1 2000000"), 0);
> +
> + ncpus = sysconf(_SC_NPROCESSORS_ONLN);
> + ASSERT_NE(-1, ncpus);
> +
> + /* ncpus+1 hogs guarantee CPU contention inside the cgroup. */
> + for (i = 0; i < ncpus + 1; i++)
> + ASSERT_GE(cg_run_nowait(self->cg, hog_cpu, NULL), 0);
> +
> + ASSERT_EQ(1, poll(&pfd, 1, PSI_POLL_TIMEOUT_MS));
> + ASSERT_NE(0, pfd.revents & POLLPRI);
> + close(fd);
> +}
> +
> +/*
> + * The flip side of cgroup_trigger_fire: with the threshold equal to the
> + * whole window, even ncpus+1 hogs must not accumulate enough stall to
> + * fire the trigger.
> + */
> +TEST_F(psi, cgroup_trigger_no_fire)
> +{
> + char *cpupress;
> + struct pollfd pfd = { .events = POLLPRI };
> + long ncpus;
> + int fd;
> + int i;
> +
> + cpupress = cg_control(self->cg, "cpu.pressure");
> + ASSERT_NE(NULL, cpupress);
> + fd = open(cpupress, O_RDWR);
> + free(cpupress);
> + ASSERT_GE(fd, 0);
> + pfd.fd = fd;
> +
> + ASSERT_GT(write_trigger(fd, "some 2000000 2000000"), 0);
> +
> + ncpus = sysconf(_SC_NPROCESSORS_ONLN);
> + ASSERT_NE(-1, ncpus);
> +
> + for (i = 0; i < ncpus + 1; i++)
> + ASSERT_GE(cg_run_nowait(self->cg, hog_cpu, NULL), 0);
> +
> + ASSERT_EQ(0, poll(&pfd, 1, PSI_POLL_TIMEOUT_MS));
> + close(fd);
> +}
> +
> +TEST_HARNESS_MAIN
> --
> 2.43.0
>
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