On Thu, Sep 3, 2026 at 12:35 AM Tao Cui <[email protected]> wrote: > > From: Tao Cui <[email protected]> > > 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 <[email protected]>
Thanks! Reviewed-by: Suren Baghdasaryan <[email protected]> > > --- > 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/[email protected]/ > v2: https://lore.kernel.org/all/[email protected]/ > v3: https://lore.kernel.org/all/[email protected]/ > v4: https://lore.kernel.org/all/[email protected]/ > v5: https://lore.kernel.org/all/[email protected]/ > --- > 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 >
