Author: mav
Date: Wed Nov 27 20:56:10 2013
New Revision: 258693
URL: http://svnweb.freebsd.org/changeset/base/258693
Log:
Make UMA to not blindly force offpage slab header allocation for large
(> 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
Modified:
head/sys/vm/uma_core.c
Modified: head/sys/vm/uma_core.c
==============================================================================
--- head/sys/vm/uma_core.c Wed Nov 27 20:20:02 2013 (r258692)
+++ head/sys/vm/uma_core.c Wed Nov 27 20:56:10 2013 (r258693)
@@ -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;
}
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