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Make UMA to not blindly force offpage slab header allocation for large

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(> PAGE_SIZE) zones.  If zone is not multiple to PAGE_SIZE, there may
be enough space for the header at the last page, so we may avoid extra
header memory allocation and hash table update/lookup.

ZFS creates bunch of odd-sized UMA zones (5120, 6144, 7168, 10240, 14336).
This change gives good use to at least some of otherwise lost memory there.

Reviewed by:	avg
This commit is contained in:
Alexander Motin 2013-11-27 20:56:10 +00:00
parent 4fe3b90bd3
commit cec48e002a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=258693
1 changed files with 16 additions and 2 deletions
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18
sys/vm/uma_core.c
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@ -1318,6 +1318,7 @@ keg_small_init(uma_keg_t keg)
static void
keg_large_init(uma_keg_t keg)
{
u_int shsize;
KASSERT(keg != NULL, ("Keg is null in keg_large_init"));
KASSERT((keg->uk_flags & UMA_ZFLAG_CACHEONLY) == 0,
@ -1334,8 +1335,21 @@ keg_large_init(uma_keg_t keg)
if (keg->uk_flags & UMA_ZFLAG_INTERNAL)
return;
keg->uk_flags |= UMA_ZONE_OFFPAGE;
if ((keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
/* Check whether we have enough space to not do OFFPAGE. */
if ((keg->uk_flags & UMA_ZONE_OFFPAGE) == 0) {
shsize = sizeof(struct uma_slab);
if (keg->uk_flags & UMA_ZONE_REFCNT)
shsize += keg->uk_ipers * sizeof(uint32_t);
if (shsize & UMA_ALIGN_PTR)
shsize = (shsize & ~UMA_ALIGN_PTR) +
(UMA_ALIGN_PTR + 1);
if ((PAGE_SIZE * keg->uk_ppera) - keg->uk_rsize < shsize)
keg->uk_flags |= UMA_ZONE_OFFPAGE;
}
if ((keg->uk_flags & UMA_ZONE_OFFPAGE) &&
(keg->uk_flags & UMA_ZONE_VTOSLAB) == 0)
keg->uk_flags |= UMA_ZONE_HASH;
}