Messages in this thread |  | | From | Konstantin Khlebnikov <> | Date | Sun, 9 Aug 2020 23:55:39 +0300 | Subject | Re: [PATCH] lib/test_lockup.c: add parameters for cond_resched inside loop |
| |
On Sun, Aug 9, 2020 at 10:06 PM Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> wrote: > > call_cond_resched_before=Y call cond_resched with resource before wait > call_cond_resched_after=Y call cond_resched with resource after wait > measure_cond_resched=Y measure maximum cond_resched time inside loop
Do you really need all of them? It seems "call_cond_resched_after" is enough for demonstration. It could be shortened to just "call_cond_resched". I see no sense in ordering before\after sleep.
Measuring time of cond_resched has vague meaning too. This just "yep, we have an overload".
> > This simulate situation where process call cond_resched() with lock held. > > Example demonstrate priority inversion issue with epbf-program, where > low priority task sheduled out while holding cgroup_mutex for a long > periods of time which blocks others programs with high priority. > > CGROUP_MUTEX=$(gawk '$3 == "cgroup_mutex" {print "0x"$1}' /proc/kallsyms) > # Emulate ebpf-application load which can hung inside cgroup_bpf_attach() > nice -20 modprobe lib/test_lockup.ko \ > time_nsecs=1000 cooldown_nsecs=100000 iterations=100000 \ > lock_mutex_ptr=$CGROUP_MUTEX \ > measure_lock_wait=Y call_cond_resched_after=Y & > > stress-ng -c $(nproc) --timeout 10s& > time mkdir /sys/fs/cgroup/blkio/a > > Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> > --- > lib/test_lockup.c | 44 +++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 43 insertions(+), 1 deletion(-) > > diff --git a/lib/test_lockup.c b/lib/test_lockup.c > index 0f81252..3e05d6e 100644 > --- a/lib/test_lockup.c > +++ b/lib/test_lockup.c > @@ -77,6 +77,18 @@ static bool call_cond_resched; > module_param(call_cond_resched, bool, 0600); > MODULE_PARM_DESC(call_cond_resched, "call cond_resched() between iterations"); > > +static bool call_cond_resched_before; > +module_param(call_cond_resched_before, bool, 0600); > +MODULE_PARM_DESC(call_cond_resched_before, "call cond_resched() before wait"); > + > +static bool call_cond_resched_after; > +module_param(call_cond_resched_after, bool, 0600); > +MODULE_PARM_DESC(call_cond_resched_after, "call cond_resched() after wait"); > + > +static bool measure_cond_resched; > +module_param(measure_cond_resched, bool, 0400); > +MODULE_PARM_DESC(measure_cond_resched, "measure cond_resched time"); > + > static bool measure_lock_wait; > module_param(measure_lock_wait, bool, 0400); > MODULE_PARM_DESC(measure_lock_wait, "measure lock wait time"); > @@ -162,6 +174,7 @@ MODULE_PARM_DESC(lock_sb_umount, "lock file -> sb -> s_umount"); > static atomic_t alloc_pages_failed = ATOMIC_INIT(0); > > static atomic64_t max_lock_wait = ATOMIC64_INIT(0); > +static atomic64_t max_cond_resched = ATOMIC64_INIT(0); > > static struct task_struct *main_task; > static int master_cpu; > @@ -346,6 +359,22 @@ static void test_wait(unsigned int secs, unsigned int nsecs) > } > } > > +static void test_cond_resched(void) > +{ > + s64 cur, old_max; > + s64 start = local_clock(); > + > + cond_resched(); > + > + cur = local_clock() - start; > + old_max = atomic64_read(&max_cond_resched); > + do { > + if (cur < old_max) > + break; > + old_max = atomic64_cmpxchg(&max_cond_resched, old_max, cur); > + } while (old_max != cur); > +} > + > static void test_lockup(bool master) > { > u64 lockup_start = local_clock(); > @@ -363,8 +392,14 @@ static void test_lockup(bool master) > if (iowait) > current->in_iowait = 1; > > + if (call_cond_resched_before) > + test_cond_resched(); > + > test_wait(time_secs, time_nsecs); > > + if (call_cond_resched_after) > + test_cond_resched(); > + > if (iowait) > current->in_iowait = 0; > > @@ -497,6 +532,7 @@ static int __init test_lockup_init(void) > > if ((wait_state != TASK_RUNNING || > (call_cond_resched && !reacquire_locks) || > + call_cond_resched_before || call_cond_resched_after || > (alloc_pages_nr && gfpflags_allow_blocking(alloc_pages_gfp))) && > (test_disable_irq || disable_softirq || disable_preempt || > lock_rcu || lock_spinlock_ptr || lock_rwlock_ptr)) { > @@ -532,7 +568,7 @@ static int __init test_lockup_init(void) > if (test_lock_sb_umount && test_inode) > lock_rwsem_ptr = (unsigned long)&test_inode->i_sb->s_umount; > > - pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s\n", > + pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s%s%s\n", > main_task->pid, time_secs, time_nsecs, > cooldown_secs, cooldown_nsecs, iterations, state, > all_cpus ? "all_cpus " : "", > @@ -545,6 +581,8 @@ static int __init test_lockup_init(void) > touch_softlockup ? "touch_softlockup " : "", > touch_hardlockup ? "touch_hardlockup " : "", > call_cond_resched ? "call_cond_resched " : "", > + call_cond_resched_before ? "call_cond_resched_before " : "", > + call_cond_resched_after ? "call_cond_resched_after " : "", > reacquire_locks ? "reacquire_locks " : ""); > > if (alloc_pages_nr) > @@ -578,6 +616,10 @@ static int __init test_lockup_init(void) > pr_notice("Maximum lock wait: %lld ns\n", > atomic64_read(&max_lock_wait)); > > + if (measure_cond_resched) > + pr_notice("Maximum cond resched time: %lld ns\n", > + atomic64_read(&max_cond_resched)); > + > if (alloc_pages_nr) > pr_notice("Page allocation failed %u times\n", > atomic_read(&alloc_pages_failed)); > -- > 2.7.4 >
|  |