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uma: Respect uk_reserve in keg_drain()

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When a reserve of free items is configured for a zone, the reserve must
not be reclaimed under memory pressure.  Modify keg_drain() to simply
respect the reserved pool.

While here remove an always-false uk_freef == NULL check (kegs that
shouldn't be drained should set _NOFREE instead), and make sure that the
keg_drain() KTR statement does not reference an uninitialized variable.

Reviewed by:	alc, rlibby
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D26772
This commit is contained in:
Mark Johnston 2020-10-19 16:57:40 +00:00
parent 1b2dcc8c54
commit f09cbea31a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=366840
1 changed files with 64 additions and 27 deletions
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91
sys/vm/uma_core.c
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@ -1415,6 +1415,63 @@ keg_free_slab(uma_keg_t keg, uma_slab_t slab, int start)
uma_total_dec(PAGE_SIZE * keg->uk_ppera);
}
static void
keg_drain_domain(uma_keg_t keg, int domain)
{
struct slabhead freeslabs;
uma_domain_t dom;
uma_slab_t slab, tmp;
uint32_t i, stofree, stokeep, partial;
dom = &keg->uk_domain[domain];
LIST_INIT(&freeslabs);
CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u",
keg->uk_name, keg, i, dom->ud_free_items);
KEG_LOCK(keg, domain);
/*
* Are the free items in partially allocated slabs sufficient to meet
* the reserve? If not, compute the number of fully free slabs that must
* be kept.
*/
partial = dom->ud_free_items - dom->ud_free_slabs * keg->uk_ipers;
if (partial < keg->uk_reserve) {
stokeep = min(dom->ud_free_slabs,
howmany(keg->uk_reserve - partial, keg->uk_ipers));
} else {
stokeep = 0;
}
stofree = dom->ud_free_slabs - stokeep;
/*
* Partition the free slabs into two sets: those that must be kept in
* order to maintain the reserve, and those that may be released back to
* the system. Since one set may be much larger than the other,
* populate the smaller of the two sets and swap them if necessary.
*/
for (i = min(stofree, stokeep); i > 0; i--) {
slab = LIST_FIRST(&dom->ud_free_slab);
LIST_REMOVE(slab, us_link);
LIST_INSERT_HEAD(&freeslabs, slab, us_link);
}
if (stofree > stokeep)
LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link);
if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) {
LIST_FOREACH(slab, &freeslabs, us_link)
UMA_HASH_REMOVE(&keg->uk_hash, slab);
}
dom->ud_free_items -= stofree * keg->uk_ipers;
dom->ud_free_slabs -= stofree;
dom->ud_pages -= stofree * keg->uk_ppera;
KEG_UNLOCK(keg, domain);
LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp)
keg_free_slab(keg, slab, keg->uk_ipers);
}
/*
* Frees pages from a keg back to the system. This is done on demand from
* the pageout daemon.
@ -1424,35 +1481,12 @@ keg_free_slab(uma_keg_t keg, uma_slab_t slab, int start)
static void
keg_drain(uma_keg_t keg)
{
struct slabhead freeslabs;
uma_domain_t dom;
uma_slab_t slab, tmp;
int i, n;
int i;
if (keg->uk_flags & UMA_ZONE_NOFREE || keg->uk_freef == NULL)
if ((keg->uk_flags & UMA_ZONE_NOFREE) != 0)
return;
for (i = 0; i < vm_ndomains; i++) {
CTR4(KTR_UMA, "keg_drain %s(%p) domain %d free items: %u",
keg->uk_name, keg, i, dom->ud_free_items);
dom = &keg->uk_domain[i];
LIST_INIT(&freeslabs);
KEG_LOCK(keg, i);
if ((keg->uk_flags & UMA_ZFLAG_HASH) != 0) {
LIST_FOREACH(slab, &dom->ud_free_slab, us_link)
UMA_HASH_REMOVE(&keg->uk_hash, slab);
}
n = dom->ud_free_slabs;
LIST_SWAP(&freeslabs, &dom->ud_free_slab, uma_slab, us_link);
dom->ud_free_slabs = 0;
dom->ud_free_items -= n * keg->uk_ipers;
dom->ud_pages -= n * keg->uk_ppera;
KEG_UNLOCK(keg, i);
LIST_FOREACH_SAFE(slab, &freeslabs, us_link, tmp)
keg_free_slab(keg, slab, keg->uk_ipers);
}
for (i = 0; i < vm_ndomains; i++)
keg_drain_domain(keg, i);
}
static void
@ -2411,6 +2445,9 @@ zone_alloc_sysctl(uma_zone_t zone, void *unused)
SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
"align", CTLFLAG_RD, &keg->uk_align, 0,
"item alignment mask");
SYSCTL_ADD_U32(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
"reserve", CTLFLAG_RD, &keg->uk_reserve, 0,
"number of reserved items");
SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(oid), OID_AUTO,
"efficiency", CTLFLAG_RD | CTLTYPE_INT | CTLFLAG_MPSAFE,
keg, 0, sysctl_handle_uma_slab_efficiency, "I",