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vm_pageout: Scale worker threads with CPUs

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Autoscale vm_pageout worker threads from r364129 with CPU count.  The
default is arbitrarily chosen to be 16 CPUs per worker thread, but can
be adjusted with the vm.pageout_cpus_per_thread tunable.

There will never be less than 1 thread per populated NUMA domain, and
the previous arbitrary upper limit (at most ncpus/2 threads per NUMA
domain) is preserved.

Care is taken to gracefully handle asymmetric NUMA nodes, such as empty
node systems (e.g., AMD 2990WX) and systems with nodes of varying size
(e.g., some larger >20 core Intel Haswell/Broadwell Xeon).

Reviewed by:	kib, markj
Sponsored by:	Isilon
Differential Revision:	https://reviews.freebsd.org/D26152
This commit is contained in:
Conrad Meyer 2020-08-25 21:36:56 +00:00
parent 60403b98b9
commit 74f5530d7a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364786
1 changed files with 31 additions and 32 deletions
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63
sys/vm/vm_pageout.c
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@ -165,11 +165,10 @@ SYSCTL_INT(_vm, OID_AUTO, pageout_update_period,
CTLFLAG_RWTUN, &vm_pageout_update_period, 0,
"Maximum active LRU update period");
/* Access with get_pageout_threads_per_domain(). */
static int pageout_threads_per_domain = 1;
SYSCTL_INT(_vm, OID_AUTO, pageout_threads_per_domain, CTLFLAG_RDTUN,
&pageout_threads_per_domain, 0,
"Number of worker threads comprising each per-domain pagedaemon");
static int pageout_cpus_per_thread = 16;
SYSCTL_INT(_vm, OID_AUTO, pageout_cpus_per_thread, CTLFLAG_RDTUN,
&pageout_cpus_per_thread, 0,
"Number of CPUs per pagedaemon worker thread");
SYSCTL_INT(_vm, OID_AUTO, lowmem_period, CTLFLAG_RWTUN, &lowmem_period, 0,
"Low memory callback period");
@ -2200,38 +2199,38 @@ vm_pageout_helper(void *arg)
}
static int
get_pageout_threads_per_domain(void)
get_pageout_threads_per_domain(const struct vm_domain *vmd)
{
static bool resolved = false;
int half_cpus_per_dom;
unsigned total_pageout_threads, eligible_cpus, domain_cpus;
/*
* This is serialized externally by the sorted autoconfig portion of
* boot.
*/
if (__predict_true(resolved))
return (pageout_threads_per_domain);
if (VM_DOMAIN_EMPTY(vmd->vmd_domain))
return (0);
/*
* Semi-arbitrarily constrain pagedaemon threads to less than half the
* total number of threads in the system as an insane upper limit.
* total number of CPUs in the system as an upper limit.
*/
half_cpus_per_dom = howmany(mp_ncpus / vm_ndomains, 2);
if (pageout_cpus_per_thread < 2)
pageout_cpus_per_thread = 2;
else if (pageout_cpus_per_thread > mp_ncpus)
pageout_cpus_per_thread = mp_ncpus;
if (pageout_threads_per_domain < 1) {
printf("Invalid tuneable vm.pageout_threads_per_domain value: "
"%d out of valid range: [1-%d]; clamping to 1\n",
pageout_threads_per_domain, half_cpus_per_dom);
pageout_threads_per_domain = 1;
} else if (pageout_threads_per_domain > half_cpus_per_dom) {
printf("Invalid tuneable vm.pageout_threads_per_domain value: "
"%d out of valid range: [1-%d]; clamping to %d\n",
pageout_threads_per_domain, half_cpus_per_dom,
half_cpus_per_dom);
pageout_threads_per_domain = half_cpus_per_dom;
}
resolved = true;
return (pageout_threads_per_domain);
total_pageout_threads = howmany(mp_ncpus, pageout_cpus_per_thread);
domain_cpus = CPU_COUNT(&cpuset_domain[vmd->vmd_domain]);
/* Pagedaemons are not run in empty domains. */
eligible_cpus = mp_ncpus;
for (unsigned i = 0; i < vm_ndomains; i++)
if (VM_DOMAIN_EMPTY(i))
eligible_cpus -= CPU_COUNT(&cpuset_domain[i]);
/*
* Assign a portion of the total pageout threads to this domain
* corresponding to the fraction of pagedaemon-eligible CPUs in the
* domain. In asymmetric NUMA systems, domains with more CPUs may be
* allocated more threads than domains with fewer CPUs.
*/
return (howmany(total_pageout_threads * domain_cpus, eligible_cpus));
}
/*
@ -2288,7 +2287,7 @@ vm_pageout_init_domain(int domain)
"pidctrl", CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "");
pidctrl_init_sysctl(&vmd->vmd_pid, SYSCTL_CHILDREN(oid));
vmd->vmd_inactive_threads = get_pageout_threads_per_domain();
vmd->vmd_inactive_threads = get_pageout_threads_per_domain(vmd);
}
static void
@ -2343,7 +2342,6 @@ vm_pageout(void)
p = curproc;
td = curthread;
pageout_threads = get_pageout_threads_per_domain();
mtx_init(&vm_oom_ratelim_mtx, "vmoomr", NULL, MTX_DEF);
swap_pager_swap_init();
@ -2363,6 +2361,7 @@ vm_pageout(void)
panic("starting pageout for domain %d: %d\n",
i, error);
}
pageout_threads = VM_DOMAIN(i)->vmd_inactive_threads;
for (j = 0; j < pageout_threads - 1; j++) {
error = kthread_add(vm_pageout_helper,
(void *)(uintptr_t)i, p, NULL, 0, 0,