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Use a precise bit count for the slab free items in UMA. This significantly

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shrinks embedded slab structures.

Reviewed by:	markj, rlibby (prior version)
Differential Revision:	https://reviews.freebsd.org/D22584
This commit is contained in:
Jeff Roberson 2019-12-02 22:44:34 +00:00
parent 0f9e06e18b
commit 9b78b1f433
5 changed files with 99 additions and 65 deletions
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4
sys/kern/subr_vmem.c
View File

@ -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

5
sys/sys/bitset.h
View File

@ -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_ */

121
sys/vm/uma_core.c
View File

@ -1200,9 +1200,9 @@ keg_alloc_slab(uma_keg_t keg, uma_zone_t zone, int domain, int flags,
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) {
@ -1485,6 +1485,46 @@ zero_init(void *mem, int size, int flags)
return (0);
}
/*
* 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.
*
@ -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);
@ -2265,38 +2314,28 @@ 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));
/*
* 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));
space / roundup2(ksize, UMA_BOOT_ALIGN));
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 *item)
/* 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 *item)
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 *item)
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 */

32
sys/vm/uma_int.h
View File

@ -139,19 +139,6 @@
/* Max waste percentage before going to off page slab management */
#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
@ -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
@ -299,6 +288,11 @@ struct uma_slab {
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);
struct uma_zone_domain {

2
sys/vm/vm_page.c
View File

@ -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