svn commit: r355315 - in head/sys: kern sys vm
Jeff Roberson
jeff at FreeBSD.org
Mon Dec 2 22:44:36 UTC 2019
Author: jeff
Date: Mon Dec 2 22:44:34 2019
New Revision: 355315
URL: https://svnweb.freebsd.org/changeset/base/355315
Log:
Use a precise bit count for the slab free items in UMA. This significantly
shrinks embedded slab structures.
Reviewed by: markj, rlibby (prior version)
Differential Revision: https://reviews.freebsd.org/D22584
Modified:
head/sys/kern/subr_vmem.c
head/sys/sys/bitset.h
head/sys/vm/uma_core.c
head/sys/vm/uma_int.h
head/sys/vm/vm_page.c
Modified: head/sys/kern/subr_vmem.c
==============================================================================
--- head/sys/kern/subr_vmem.c Mon Dec 2 22:42:05 2019 (r355314)
+++ head/sys/kern/subr_vmem.c Mon Dec 2 22:44:34 2019 (r355315)
@@ -670,8 +670,8 @@ int
vmem_startup_count(void)
{
- return (howmany(BT_MAXALLOC,
- UMA_SLAB_SPACE / sizeof(struct vmem_btag)));
+ return (howmany(BT_MAXALLOC, slab_ipers(sizeof(struct vmem_btag),
+ UMA_ALIGN_PTR)));
}
#endif
Modified: head/sys/sys/bitset.h
==============================================================================
--- head/sys/sys/bitset.h Mon Dec 2 22:42:05 2019 (r355314)
+++ head/sys/sys/bitset.h Mon Dec 2 22:44:34 2019 (r355315)
@@ -246,10 +246,11 @@
#define BITSET_FSET(n) \
[ 0 ... ((n) - 1) ] = (-1L)
+#define BITSET_SIZE(_s) (__bitset_words((_s)) * sizeof(long))
+
/*
* Dynamically allocate a bitset.
*/
-#define BITSET_ALLOC(_s, mt, mf) \
- malloc(__bitset_words(_s) * sizeof(long), mt, (mf))
+#define BITSET_ALLOC(_s, mt, mf) malloc(BITSET_SIZE((_s)), mt, (mf))
#endif /* !_SYS_BITSET_H_ */
Modified: head/sys/vm/uma_core.c
==============================================================================
--- head/sys/vm/uma_core.c Mon Dec 2 22:42:05 2019 (r355314)
+++ head/sys/vm/uma_core.c Mon Dec 2 22:44:34 2019 (r355315)
@@ -1200,9 +1200,9 @@ keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int dom
slab->us_freecount = keg->uk_ipers;
slab->us_flags = sflags;
slab->us_domain = domain;
- BIT_FILL(SLAB_SETSIZE, &slab->us_free);
+ BIT_FILL(keg->uk_ipers, &slab->us_free);
#ifdef INVARIANTS
- BIT_ZERO(SLAB_SETSIZE, &slab->us_debugfree);
+ BIT_ZERO(SLAB_MAX_SETSIZE, &slab->us_debugfree);
#endif
if (keg->uk_init != NULL) {
@@ -1486,6 +1486,46 @@ zero_init(void *mem, int size, int flags)
}
/*
+ * Actual size of embedded struct slab (!OFFPAGE).
+ */
+size_t
+slab_sizeof(int nitems)
+{
+ size_t s;
+
+ s = sizeof(struct uma_slab) + BITSET_SIZE(nitems);
+ return (roundup(s, UMA_ALIGN_PTR + 1));
+}
+
+/*
+ * Size of memory for embedded slabs (!OFFPAGE).
+ */
+size_t
+slab_space(int nitems)
+{
+ return (UMA_SLAB_SIZE - slab_sizeof(nitems));
+}
+
+/*
+ * Compute the number of items that will fit in an embedded (!OFFPAGE) slab
+ * with a given size and alignment.
+ */
+int
+slab_ipers(size_t size, int align)
+{
+ int rsize;
+ int nitems;
+
+ /*
+ * Compute the ideal number of items that will fit in a page and
+ * then compute the actual number based on a bitset nitems wide.
+ */
+ rsize = roundup(size, align + 1);
+ nitems = UMA_SLAB_SIZE / rsize;
+ return (slab_space(nitems) / rsize);
+}
+
+/*
* Finish creating a small uma keg. This calculates ipers, and the keg size.
*
* Arguments
@@ -1519,20 +1559,25 @@ keg_small_init(uma_keg_t keg)
* allocation bits for we round it up.
*/
rsize = keg->uk_size;
- if (rsize < slabsize / SLAB_SETSIZE)
- rsize = slabsize / SLAB_SETSIZE;
+ if (rsize < slabsize / SLAB_MAX_SETSIZE)
+ rsize = slabsize / SLAB_MAX_SETSIZE;
if (rsize & keg->uk_align)
- rsize = (rsize & ~keg->uk_align) + (keg->uk_align + 1);
+ rsize = roundup(rsize, keg->uk_align + 1);
keg->uk_rsize = rsize;
KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0 ||
keg->uk_rsize < UMA_PCPU_ALLOC_SIZE,
("%s: size %u too large", __func__, keg->uk_rsize));
+ /*
+ * Use a pessimistic bit count for shsize. It may be possible to
+ * squeeze one more item in for very particular sizes if we were
+ * to loop and reduce the bitsize if there is waste.
+ */
if (keg->uk_flags & UMA_ZONE_OFFPAGE)
shsize = 0;
else
- shsize = SIZEOF_UMA_SLAB;
+ shsize = slab_sizeof(slabsize / rsize);
if (rsize <= slabsize - shsize)
keg->uk_ipers = (slabsize - shsize) / rsize;
@@ -1543,7 +1588,7 @@ keg_small_init(uma_keg_t keg)
("%s: size %u greater than slab", __func__, keg->uk_size));
keg->uk_ipers = 1;
}
- KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
+ KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_MAX_SETSIZE,
("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
memused = keg->uk_ipers * rsize + shsize;
@@ -1571,7 +1616,7 @@ keg_small_init(uma_keg_t keg)
if ((wastedspace >= slabsize / UMA_MAX_WASTE) &&
(keg->uk_ipers < (slabsize / keg->uk_rsize))) {
keg->uk_ipers = slabsize / keg->uk_rsize;
- KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE,
+ KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_MAX_SETSIZE,
("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
CTR6(KTR_UMA, "UMA decided we need offpage slab headers for "
"keg: %s(%p), calculated wastedspace = %d, "
@@ -1620,7 +1665,8 @@ keg_large_init(uma_keg_t keg)
/* Check whether we have enough space to not do OFFPAGE. */
if ((keg->uk_flags & UMA_ZONE_OFFPAGE) == 0 &&
- PAGE_SIZE * keg->uk_ppera - keg->uk_rsize < SIZEOF_UMA_SLAB) {
+ PAGE_SIZE * keg->uk_ppera - keg->uk_rsize <
+ slab_sizeof(SLAB_MIN_SETSIZE)) {
/*
* We can't do OFFPAGE if we're internal, in which case
* we need an extra page per allocation to contain the
@@ -1667,7 +1713,7 @@ keg_cachespread_init(uma_keg_t keg)
keg->uk_ppera = pages;
keg->uk_ipers = ((pages * PAGE_SIZE) + trailer) / rsize;
keg->uk_flags |= UMA_ZONE_OFFPAGE | UMA_ZONE_VTOSLAB;
- KASSERT(keg->uk_ipers <= SLAB_SETSIZE,
+ KASSERT(keg->uk_ipers <= SLAB_MAX_SETSIZE,
("%s: keg->uk_ipers too high(%d) increase max_ipers", __func__,
keg->uk_ipers));
}
@@ -1730,7 +1776,7 @@ keg_ctor(void *mem, int size, void *udata, int flags)
if (keg->uk_flags & UMA_ZONE_CACHESPREAD) {
keg_cachespread_init(keg);
} else {
- if (keg->uk_size > UMA_SLAB_SPACE)
+ if (keg->uk_size > slab_space(SLAB_MIN_SETSIZE))
keg_large_init(keg);
else
keg_small_init(keg);
@@ -1770,11 +1816,14 @@ 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. See SIZEOF_UMA_SLAB
- * macro definition.
+ * figure out where in each page it goes. See slab_sizeof
+ * definition.
*/
if (!(keg->uk_flags & UMA_ZONE_OFFPAGE)) {
- keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - SIZEOF_UMA_SLAB;
+ size_t shsize;
+
+ shsize = slab_sizeof(keg->uk_ipers);
+ keg->uk_pgoff = (PAGE_SIZE * keg->uk_ppera) - shsize;
/*
* The only way the following is possible is if with our
* UMA_ALIGN_PTR adjustments we are now bigger than
@@ -1782,8 +1831,7 @@ keg_ctor(void *mem, int size, void *udata, int flags)
* mathematically possible for all cases, so we make
* sure here anyway.
*/
- KASSERT(keg->uk_pgoff + sizeof(struct uma_slab) <=
- PAGE_SIZE * keg->uk_ppera,
+ KASSERT(keg->uk_pgoff + shsize <= 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));
}
@@ -2245,6 +2293,7 @@ int
uma_startup_count(int vm_zones)
{
int zones, pages;
+ size_t space, size;
ksize = sizeof(struct uma_keg) +
(sizeof(struct uma_domain) * vm_ndomains);
@@ -2265,39 +2314,29 @@ uma_startup_count(int vm_zones)
zones = UMA_BOOT_ZONES + vm_zones;
vm_zones = 0;
#endif
+ size = slab_sizeof(SLAB_MAX_SETSIZE);
+ space = slab_space(SLAB_MAX_SETSIZE);
/* Memory for the rest of startup zones, UMA and VM, ... */
- if (zsize > UMA_SLAB_SPACE) {
+ if (zsize > space) {
/* See keg_large_init(). */
u_int ppera;
ppera = howmany(roundup2(zsize, UMA_BOOT_ALIGN), PAGE_SIZE);
- if (PAGE_SIZE * ppera - roundup2(zsize, UMA_BOOT_ALIGN) <
- SIZEOF_UMA_SLAB)
+ if (PAGE_SIZE * ppera - roundup2(zsize, UMA_BOOT_ALIGN) < size)
ppera++;
pages += (zones + vm_zones) * ppera;
- } else if (roundup2(zsize, UMA_BOOT_ALIGN) > UMA_SLAB_SPACE)
+ } else if (roundup2(zsize, UMA_BOOT_ALIGN) > space)
/* See keg_small_init() special case for uk_ppera = 1. */
pages += zones;
else
pages += howmany(zones,
- UMA_SLAB_SPACE / roundup2(zsize, UMA_BOOT_ALIGN));
+ space / roundup2(zsize, UMA_BOOT_ALIGN));
/* ... and their kegs. Note that zone of zones allocates a keg! */
pages += howmany(zones + 1,
- UMA_SLAB_SPACE / roundup2(ksize, UMA_BOOT_ALIGN));
+ space / roundup2(ksize, UMA_BOOT_ALIGN));
- /*
- * Most of startup zones are not going to be offpages, that's
- * why we use UMA_SLAB_SPACE instead of UMA_SLAB_SIZE in all
- * calculations. Some large bucket zones will be offpage, and
- * thus will allocate hashes. We take conservative approach
- * and assume that all zones may allocate hash. This may give
- * us some positive inaccuracy, usually an extra single page.
- */
- pages += howmany(zones, UMA_SLAB_SPACE /
- (sizeof(struct slabhead *) * UMA_HASH_SIZE_INIT));
-
return (pages);
}
@@ -2355,7 +2394,7 @@ uma_startup(void *mem, int npages)
/* Now make a zone for slab headers */
slabzone = uma_zcreate("UMA Slabs",
- sizeof(struct uma_slab),
+ slab_sizeof(SLAB_MAX_SETSIZE),
NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, UMA_ZFLAG_INTERNAL);
@@ -3056,8 +3095,8 @@ slab_alloc_item(uma_keg_t keg, uma_slab_t slab)
KEG_LOCK_ASSERT(keg);
- freei = BIT_FFS(SLAB_SETSIZE, &slab->us_free) - 1;
- BIT_CLR(SLAB_SETSIZE, freei, &slab->us_free);
+ freei = BIT_FFS(keg->uk_ipers, &slab->us_free) - 1;
+ BIT_CLR(keg->uk_ipers, freei, &slab->us_free);
item = slab->us_data + (keg->uk_rsize * freei);
slab->us_freecount--;
keg->uk_free--;
@@ -3569,7 +3608,7 @@ slab_free_item(uma_zone_t zone, uma_slab_t slab, void
/* Slab management. */
freei = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
- BIT_SET(SLAB_SETSIZE, freei, &slab->us_free);
+ BIT_SET(keg->uk_ipers, freei, &slab->us_free);
slab->us_freecount++;
/* Keg statistics. */
@@ -4450,10 +4489,10 @@ uma_dbg_alloc(uma_zone_t zone, uma_slab_t slab, void *
keg = zone->uz_keg;
freei = ((uintptr_t)item - (uintptr_t)slab->us_data) / keg->uk_rsize;
- if (BIT_ISSET(SLAB_SETSIZE, freei, &slab->us_debugfree))
+ if (BIT_ISSET(SLAB_MAX_SETSIZE, freei, &slab->us_debugfree))
panic("Duplicate alloc of %p from zone %p(%s) slab %p(%d)\n",
item, zone, zone->uz_name, slab, freei);
- BIT_SET_ATOMIC(SLAB_SETSIZE, freei, &slab->us_debugfree);
+ BIT_SET_ATOMIC(SLAB_MAX_SETSIZE, freei, &slab->us_debugfree);
return;
}
@@ -4486,11 +4525,11 @@ uma_dbg_free(uma_zone_t zone, uma_slab_t slab, void *i
panic("Unaligned free of %p from zone %p(%s) slab %p(%d)\n",
item, zone, zone->uz_name, slab, freei);
- if (!BIT_ISSET(SLAB_SETSIZE, freei, &slab->us_debugfree))
+ if (!BIT_ISSET(SLAB_MAX_SETSIZE, freei, &slab->us_debugfree))
panic("Duplicate free of %p from zone %p(%s) slab %p(%d)\n",
item, zone, zone->uz_name, slab, freei);
- BIT_CLR_ATOMIC(SLAB_SETSIZE, freei, &slab->us_debugfree);
+ BIT_CLR_ATOMIC(SLAB_MAX_SETSIZE, freei, &slab->us_debugfree);
}
#endif /* INVARIANTS */
Modified: head/sys/vm/uma_int.h
==============================================================================
--- head/sys/vm/uma_int.h Mon Dec 2 22:42:05 2019 (r355314)
+++ head/sys/vm/uma_int.h Mon Dec 2 22:44:34 2019 (r355315)
@@ -140,19 +140,6 @@
#define UMA_MAX_WASTE 10
/*
- * Actual size of uma_slab when it is placed at an end of a page
- * with pointer sized alignment requirement.
- */
-#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
* size of the hash table for uma_slabs that are managed off page. This hash
* does expand by powers of two. Currently it doesn't get smaller.
@@ -273,8 +260,10 @@ typedef struct uma_keg * uma_keg_t;
/*
* Free bits per-slab.
*/
-#define SLAB_SETSIZE (PAGE_SIZE / UMA_SMALLEST_UNIT)
-BITSET_DEFINE(slabbits, SLAB_SETSIZE);
+#define SLAB_MAX_SETSIZE (PAGE_SIZE / UMA_SMALLEST_UNIT)
+#define SLAB_MIN_SETSIZE _BITSET_BITS
+BITSET_DEFINE(slabbits, SLAB_MAX_SETSIZE);
+BITSET_DEFINE(noslabbits, 0);
/*
* The slab structure manages a single contiguous allocation from backing
@@ -284,13 +273,13 @@ struct uma_slab {
LIST_ENTRY(uma_slab) us_link; /* slabs in zone */
SLIST_ENTRY(uma_slab) us_hlink; /* Link for hash table */
uint8_t *us_data; /* First item */
- struct slabbits us_free; /* Free bitmask. */
-#ifdef INVARIANTS
- struct slabbits us_debugfree; /* Debug bitmask. */
-#endif
uint16_t us_freecount; /* How many are free? */
uint8_t us_flags; /* Page flags see uma.h */
uint8_t us_domain; /* Backing NUMA domain. */
+#ifdef INVARIANTS
+ struct slabbits us_debugfree; /* Debug bitmask. */
+#endif
+ struct noslabbits us_free; /* Free bitmask. */
};
#if MAXMEMDOM >= 255
@@ -298,6 +287,11 @@ struct uma_slab {
#endif
typedef struct uma_slab * uma_slab_t;
+
+/* These three functions are for embedded (!OFFPAGE) use only. */
+size_t slab_sizeof(int nitems);
+size_t slab_space(int nitems);
+int slab_ipers(size_t size, int align);
TAILQ_HEAD(uma_bucketlist, uma_bucket);
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Mon Dec 2 22:42:05 2019 (r355314)
+++ head/sys/vm/vm_page.c Mon Dec 2 22:44:34 2019 (r355315)
@@ -600,7 +600,7 @@ vm_page_startup(vm_offset_t vaddr)
boot_pages += vmem_startup_count();
/* vm_map_startup() calls uma_prealloc(). */
boot_pages += howmany(MAX_KMAP,
- UMA_SLAB_SPACE / sizeof(struct vm_map));
+ slab_ipers(sizeof(struct vm_map), UMA_ALIGN_PTR));
/*
* Before going fully functional kmem_init() does allocation
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