Author: glebius
Date: Wed Nov 28 19:17:27 2018
New Revision: 341162
URL: https://svnweb.freebsd.org/changeset/base/341162
Log:
For not offpage zones the slab is placed at the end of page. Keg's uk_pgoff
is calculated to guarantee that struct uma_slab is placed at pointer size
alignment. Calculation of real struct uma_slab size is done in keg_ctor()
and yet again in keg_large_init(), to check if we need an extra page. This
calculation can actually be performed at compile time.
- Add SIZEOF_UMA_SLAB macro to calculate size of struct uma_slab placed at
an end of a page with alignment requirement.
- Use SIZEOF_UMA_SLAB in keg_ctor() and in keg_large_init(). This is a not
a functional change.
- Use SIZEOF_UMA_SLAB in UMA_SLAB_SPACE definition and in keg_small_init().
This is a potential bugfix, but in reality I don't think there are any
systems affected, since compiler aligns struct uma_slab anyway.
Modified:
head/sys/vm/uma_core.c
head/sys/vm/uma_int.h
Modified: head/sys/vm/uma_core.c
==============================================================================
--- head/sys/vm/uma_core.c Wed Nov 28 18:42:42 2018 (r341161)
+++ head/sys/vm/uma_core.c Wed Nov 28 19:17:27 2018 (r341162)
@@ -1453,7 +1453,7 @@ keg_small_init(uma_keg_t keg)
if (keg->uk_flags & UMA_ZONE_OFFPAGE)
shsize = 0;
else
- shsize = sizeof(struct uma_slab);
+ shsize = SIZEOF_UMA_SLAB;
if (rsize <= slabsize - shsize)
keg->uk_ipers = (slabsize - shsize) / rsize;
@@ -1523,7 +1523,6 @@ 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,
@@ -1536,23 +1535,17 @@ keg_large_init(uma_keg_t keg)
keg->uk_rsize = keg->uk_size;
/* Check whether we have enough space to not do OFFPAGE. */
- if ((keg->uk_flags & UMA_ZONE_OFFPAGE) == 0) {
- shsize = sizeof(struct uma_slab);
- if (shsize & UMA_ALIGN_PTR)
- shsize = (shsize & ~UMA_ALIGN_PTR) +
- (UMA_ALIGN_PTR + 1);
-
- if (PAGE_SIZE * keg->uk_ppera - keg->uk_rsize < shsize) {
- /*
- * We can't do OFFPAGE if we're internal, in which case
- * we need an extra page per allocation to contain the
- * slab header.
- */
- if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) == 0)
- keg->uk_flags |= UMA_ZONE_OFFPAGE;
- else
- keg->uk_ppera++;
- }
+ if ((keg->uk_flags & UMA_ZONE_OFFPAGE) == 0 &&
+ PAGE_SIZE * keg->uk_ppera - keg->uk_rsize < SIZEOF_UMA_SLAB) {
+ /*
+ * We can't do OFFPAGE if we're internal, in which case
+ * we need an extra page per allocation to contain the
+ * slab header.
+ */
+ if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) == 0)
+ keg->uk_flags |= UMA_ZONE_OFFPAGE;
+ else
+ keg->uk_ppera++;
}
if ((keg->uk_flags & UMA_ZONE_OFFPAGE) &&
@@ -1693,20 +1686,11 @@ keg_ctor(void *mem, int size, void *udata, int flags)
/*
* If we're putting the slab header in the actual page we need to
- * figure out where in each page it goes. This calculates a right
- * justified offset into the memory on an ALIGN_PTR boundary.
+ * figure out where in each page it goes. See SIZEOF_UMA_SLAB
+ * macro definition.
*/
if (!(keg->uk_flags & UMA_ZONE_OFFPAGE)) {
- u_int totsize;
-
- /* Size of the slab struct and free list */
- totsize = sizeof(struct uma_slab);
-
- if (totsize & UMA_ALIGN_PTR)
- totsize = (totsize & ~UMA_ALIGN_PTR) +
- (UMA_ALIGN_PTR + 1);
- keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - totsize;
-
+ keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - SIZEOF_UMA_SLAB;
/*
* The only way the following is possible is if with our
* UMA_ALIGN_PTR adjustments we are now bigger than
@@ -1714,13 +1698,10 @@ keg_ctor(void *mem, int size, void *udata, int flags)
* mathematically possible for all cases, so we make
* sure here anyway.
*/
- totsize = keg->uk_pgoff + sizeof(struct uma_slab);
- if (totsize > PAGE_SIZE * keg->uk_ppera) {
- printf("zone %s ipers %d rsize %d size %d\n",
- zone->uz_name, keg->uk_ipers, keg->uk_rsize,
- keg->uk_size);
- panic("UMA slab won't fit.");
- }
+ KASSERT(keg->uk_pgoff + sizeof(struct uma_slab) <=
+ PAGE_SIZE * keg->uk_ppera,
+ ("zone %s ipers %d rsize %d size %d slab won't fit",
+ zone->uz_name, keg->uk_ipers, keg->uk_rsize, keg->uk_size));
}
if (keg->uk_flags & UMA_ZONE_HASH)
Modified: head/sys/vm/uma_int.h
==============================================================================
--- head/sys/vm/uma_int.h Wed Nov 28 18:42:42 2018 (r341161)
+++ head/sys/vm/uma_int.h Wed Nov 28 19:17:27 2018 (r341162)
@@ -139,9 +139,17 @@
#define UMA_MAX_WASTE 10
/*
- * Size of memory in a not offpage slab available for actual items.
+ * Actual size of uma_slab when it is placed at an end of a page
+ * with pointer sized alignment requirement.
*/
-#define UMA_SLAB_SPACE (UMA_SLAB_SIZE - sizeof(struct uma_slab))
+#define SIZEOF_UMA_SLAB ((sizeof(struct uma_slab) & UMA_ALIGN_PTR) ?
\
+ (sizeof(struct uma_slab) & ~UMA_ALIGN_PTR) + \
+ (UMA_ALIGN_PTR + 1) : sizeof(struct uma_slab))
+
+/*
+ * Size of memory in a not offpage single page slab available for actual items.
+ */
+#define UMA_SLAB_SPACE (PAGE_SIZE - SIZEOF_UMA_SLAB)
/*
* I doubt there will be many cases where this is exceeded. This is the initial
_______________________________________________
svn-src-head@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
