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thread: numa-aware zombie reaping

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The current global list is a significant problem, in particular induces a lot
of cross-domain thread frees. When running poudriere on a 2 domain box about
half of all frees were of that nature.

Patch below introduces per-domain thread data containing zombie lists and
domain-aware reaping. By default it only reaps from the current domain, only
reaping from others if there is free TID shortage.

A dedicated callout is introduced to reap lingering threads if there happens
to be no activity.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D27185
This commit is contained in:
Mateusz Guzik 2020-11-19 10:00:48 +00:00
parent 02a6de7789
commit d116b9f1ad
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=367842
1 changed files with 122 additions and 18 deletions
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140
sys/kern/kern_thread.c
View File

@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/turnstile.h>
#include <sys/taskqueue.h>
#include <sys/ktr.h>
#include <sys/rwlock.h>
#include <sys/umtx.h>
@ -64,9 +65,11 @@ __FBSDID("$FreeBSD$");
#include <security/audit/audit.h>
#include <vm/pmap.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <vm/vm_phys.h>
#include <sys/eventhandler.h>
/*
@ -128,9 +131,20 @@ SDT_PROBE_DEFINE(proc, , , lwp__exit);
*/
static uma_zone_t thread_zone;
static __exclusive_cache_line struct thread *thread_zombies;
struct thread_domain_data {
struct thread *tdd_zombies;
int tdd_reapticks;
} __aligned(CACHE_LINE_SIZE);
static struct thread_domain_data thread_domain_data[MAXMEMDOM];
static struct task thread_reap_task;
static struct callout thread_reap_callout;
static void thread_zombie(struct thread *);
static void thread_reap_all(void);
static void thread_reap_task_cb(void *, int);
static void thread_reap_callout_cb(void *);
static int thread_unsuspend_one(struct thread *td, struct proc *p,
bool boundary);
static void thread_free_batched(struct thread *td);
@ -159,30 +173,45 @@ EVENTHANDLER_LIST_DEFINE(thread_init);
EVENTHANDLER_LIST_DEFINE(thread_fini);
static bool
thread_count_inc(void)
thread_count_inc_try(void)
{
static struct timeval lastfail;
static int curfail;
int nthreads_new;
thread_reap();
nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
if (nthreads_new >= maxthread - 100) {
if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
nthreads_new >= maxthread) {
atomic_subtract_int(&nthreads, 1);
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxthread limit exceeded by uid %u "
"(pid %d); consider increasing kern.maxthread\n",
curthread->td_ucred->cr_ruid, curproc->p_pid);
}
return (false);
}
}
return (true);
}
static bool
thread_count_inc(void)
{
static struct timeval lastfail;
static int curfail;
thread_reap();
if (thread_count_inc_try()) {
return (true);
}
thread_reap_all();
if (thread_count_inc_try()) {
return (true);
}
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxthread limit exceeded by uid %u "
"(pid %d); consider increasing kern.maxthread\n",
curthread->td_ucred->cr_ruid, curproc->p_pid);
}
return (false);
}
static void
thread_count_sub(int n)
{
@ -500,6 +529,10 @@ threadinit(void)
M_TIDHASH, M_WAITOK | M_ZERO);
for (i = 0; i < tidhashlock + 1; i++)
rw_init(&tidhashtbl_lock[i], "tidhash");
TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL);
callout_init(&thread_reap_callout, 1);
callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
}
/*
@ -508,12 +541,14 @@ threadinit(void)
void
thread_zombie(struct thread *td)
{
struct thread_domain_data *tdd;
struct thread *ztd;
ztd = atomic_load_ptr(&thread_zombies);
tdd = &thread_domain_data[vm_phys_domain(vtophys(td))];
ztd = atomic_load_ptr(&tdd->tdd_zombies);
for (;;) {
td->td_zombie = ztd;
if (atomic_fcmpset_rel_ptr((uintptr_t *)&thread_zombies,
if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
(uintptr_t *)&ztd, (uintptr_t)td))
break;
continue;
@ -531,10 +566,10 @@ thread_stash(struct thread *td)
}
/*
* Reap zombie threads.
* Reap zombies from passed domain.
*/
void
thread_reap(void)
static void
thread_reap_domain(struct thread_domain_data *tdd)
{
struct thread *itd, *ntd;
struct tidbatch tidbatch;
@ -547,19 +582,26 @@ thread_reap(void)
* Reading upfront is pessimal if followed by concurrent atomic_swap,
* but most of the time the list is empty.
*/
if (thread_zombies == NULL)
if (tdd->tdd_zombies == NULL)
return;
itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&thread_zombies,
itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
(uintptr_t)NULL);
if (itd == NULL)
return;
/*
* Multiple CPUs can get here, the race is fine as ticks is only
* advisory.
*/
tdd->tdd_reapticks = ticks;
tidbatch_prep(&tidbatch);
credbatch_prep(&credbatch);
tdcount = 0;
lim = NULL;
limcount = 0;
while (itd != NULL) {
ntd = itd->td_zombie;
EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
@ -594,6 +636,68 @@ thread_reap(void)
lim_freen(lim, limcount);
}
/*
* Reap zombies from all domains.
*/
static void
thread_reap_all(void)
{
struct thread_domain_data *tdd;
int i, domain;
domain = PCPU_GET(domain);
for (i = 0; i < vm_ndomains; i++) {
tdd = &thread_domain_data[(i + domain) % vm_ndomains];
thread_reap_domain(tdd);
}
}
/*
* Reap zombies from local domain.
*/
void
thread_reap(void)
{
struct thread_domain_data *tdd;
int domain;
domain = PCPU_GET(domain);
tdd = &thread_domain_data[domain];
thread_reap_domain(tdd);
}
static void
thread_reap_task_cb(void *arg __unused, int pending __unused)
{
thread_reap_all();
}
static void
thread_reap_callout_cb(void *arg __unused)
{
struct thread_domain_data *tdd;
int i, cticks, lticks;
bool wantreap;
wantreap = false;
cticks = atomic_load_int(&ticks);
for (i = 0; i < vm_ndomains; i++) {
tdd = &thread_domain_data[i];
lticks = tdd->tdd_reapticks;
if (tdd->tdd_zombies != NULL &&
(u_int)(cticks - lticks) > 5 * hz) {
wantreap = true;
break;
}
}
if (wantreap)
taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
}
/*
* Allocate a thread.
*/