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uma: unify layout paths and improve efficiency

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Unify the keg layout selection paths (keg_small_init, keg_large_init,
keg_cachespread_init), and slightly improve memory efficiecy by:
 - using the padding of the final item to store the slab header,
 - not going OFFPAGE if we have a choice unless it improves efficiency.

Reviewed by:	jeff, markj
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D23048
This commit is contained in:
Ryan Libby 2020-01-09 02:03:17 +00:00
parent 54c5ae804f
commit 4a8b575c6b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=356535
2 changed files with 148 additions and 176 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

321
sys/vm/uma_core.c
View File

@ -258,8 +258,6 @@ static void keg_dtor(void *, int, void *);
static int zone_ctor(void *, int, void *, int);
static void zone_dtor(void *, int, void *);
static int zero_init(void *, int, int);
static void keg_small_init(uma_keg_t keg);
static void keg_large_init(uma_keg_t keg);
static void zone_foreach(void (*zfunc)(uma_zone_t, void *), void *);
static void zone_timeout(uma_zone_t zone, void *);
static int hash_alloc(struct uma_hash *, u_int);
@ -1669,27 +1667,61 @@ slab_space(int nitems)
return (UMA_SLAB_SIZE - slab_sizeof(nitems));
}
#define UMA_FIXPT_SHIFT 31
#define UMA_FRAC_FIXPT(n, d) \
((uint32_t)(((uint64_t)(n) << UMA_FIXPT_SHIFT) / (d)))
#define UMA_FIXPT_PCT(f) \
((u_int)(((uint64_t)100 * (f)) >> UMA_FIXPT_SHIFT))
#define UMA_PCT_FIXPT(pct) UMA_FRAC_FIXPT((pct), 100)
#define UMA_MIN_EFF UMA_PCT_FIXPT(100 - UMA_MAX_WASTE)
/*
* Compute the number of items that will fit in an embedded (!OFFPAGE) slab
* with a given size and alignment.
* Compute the number of items that will fit in a slab. If hdr is true, the
* item count may be limited to provide space in the slab for an inline slab
* header. Otherwise, all slab space will be provided for item storage.
*/
static u_int
slab_ipers_hdr(u_int size, u_int rsize, u_int slabsize, bool hdr)
{
u_int ipers;
u_int padpi;
/* The padding between items is not needed after the last item. */
padpi = rsize - size;
if (hdr) {
/*
* Start with the maximum item count and remove items until
* the slab header first alongside the allocatable memory.
*/
for (ipers = MIN(SLAB_MAX_SETSIZE,
(slabsize + padpi - slab_sizeof(1)) / rsize);
ipers > 0 &&
ipers * rsize - padpi + slab_sizeof(ipers) > slabsize;
ipers--)
continue;
} else {
ipers = MIN((slabsize + padpi) / rsize, SLAB_MAX_SETSIZE);
}
return (ipers);
}
/*
* Compute the number of items that will fit in a slab for a startup zone.
*/
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);
rsize = roundup(size, align + 1); /* Assume no CACHESPREAD */
return (slab_ipers_hdr(size, rsize, UMA_SLAB_SIZE, true));
}
/*
* Finish creating a small uma keg. This calculates ipers, and the keg size.
* Determine the format of a uma keg. This determines where the slab header
* will be placed (inline or offpage) and calculates ipers, rsize, and ppera.
*
* Arguments
* keg The zone we should initialize
@ -1698,65 +1730,76 @@ slab_ipers(size_t size, int align)
* Nothing
*/
static void
keg_small_init(uma_keg_t keg)
keg_layout(uma_keg_t keg)
{
u_int alignsize;
u_int eff;
u_int eff_offpage;
u_int format;
u_int ipers;
u_int ipers_offpage;
u_int pages;
u_int rsize;
u_int memused;
u_int wastedspace;
u_int shsize;
u_int slabsize;
if (keg->uk_flags & UMA_ZONE_PCPU) {
u_int ncpus = (mp_maxid + 1) ? (mp_maxid + 1) : MAXCPU;
KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0 ||
(keg->uk_size <= UMA_PCPU_ALLOC_SIZE &&
(keg->uk_flags & UMA_ZONE_CACHESPREAD) == 0),
("%s: cannot configure for PCPU: keg=%s, size=%u, flags=0x%b",
__func__, keg->uk_name, keg->uk_size, keg->uk_flags,
PRINT_UMA_ZFLAGS));
KASSERT((keg->uk_flags &
(UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY)) == 0 ||
(keg->uk_flags & (UMA_ZONE_NOTOUCH | UMA_ZONE_PCPU)) == 0,
("%s: incompatible flags 0x%b", __func__, keg->uk_flags,
PRINT_UMA_ZFLAGS));
slabsize = UMA_PCPU_ALLOC_SIZE;
keg->uk_ppera = ncpus;
} else {
slabsize = UMA_SLAB_SIZE;
keg->uk_ppera = 1;
}
alignsize = keg->uk_align + 1;
format = 0;
ipers = 0;
/*
* Calculate the size of each allocation (rsize) according to
* alignment. If the requested size is smaller than we have
* allocation bits for we round it up.
*/
rsize = keg->uk_size;
if (rsize < slabsize / SLAB_MAX_SETSIZE)
rsize = slabsize / SLAB_MAX_SETSIZE;
if (rsize & keg->uk_align)
rsize = roundup(rsize, keg->uk_align + 1);
keg->uk_rsize = rsize;
rsize = MAX(keg->uk_size, UMA_SLAB_SIZE / SLAB_MAX_SETSIZE);
rsize = roundup2(rsize, alignsize);
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_NOTOUCH | UMA_ZONE_PCPU)) {
keg->uk_flags |= UMA_ZFLAG_OFFPAGE;
shsize = 0;
} else
shsize = slab_sizeof(slabsize / rsize);
if (rsize <= slabsize - shsize)
keg->uk_ipers = (slabsize - shsize) / rsize;
else {
/* Handle special case when we have 1 item per slab, so
* alignment requirement can be relaxed. */
KASSERT(keg->uk_size <= slabsize - shsize,
("%s: size %u greater than slab", __func__, keg->uk_size));
keg->uk_ipers = 1;
if ((keg->uk_flags & UMA_ZONE_PCPU) != 0) {
slabsize = UMA_PCPU_ALLOC_SIZE;
pages = mp_maxid + 1;
} else if ((keg->uk_flags & UMA_ZONE_CACHESPREAD) != 0) {
/*
* We want one item to start on every align boundary in a page.
* To do this we will span pages. We will also extend the item
* by the size of align if it is an even multiple of align.
* Otherwise, it would fall on the same boundary every time.
*/
if ((rsize & alignsize) == 0)
rsize += alignsize;
slabsize = rsize * (PAGE_SIZE / alignsize);
slabsize = MIN(slabsize, rsize * SLAB_MAX_SETSIZE);
slabsize = MIN(slabsize, UMA_CACHESPREAD_MAX_SIZE);
pages = howmany(slabsize, PAGE_SIZE);
slabsize = ptoa(pages);
} else {
/*
* Choose a slab size of as many pages as it takes to represent
* a single item. We will then try to fit as many additional
* items into the slab as possible. At some point, we may want
* to increase the slab size for awkward item sizes in order to
* increase efficiency.
*/
pages = howmany(keg->uk_size, PAGE_SIZE);
slabsize = ptoa(pages);
}
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;
wastedspace = slabsize - memused;
/* Evaluate an inline slab layout. */
if ((keg->uk_flags & (UMA_ZONE_NOTOUCH | UMA_ZONE_PCPU)) == 0)
ipers = slab_ipers_hdr(keg->uk_size, rsize, slabsize, true);
/* TODO: vm_page-embedded slab. */
/*
* We can't do OFFPAGE if we're internal or if we've been
@ -1765,130 +1808,63 @@ keg_small_init(uma_keg_t keg)
* want to do if we're UMA_ZFLAG_CACHEONLY as a result
* of UMA_ZONE_VM, which clearly forbids it.
*/
if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) ||
(keg->uk_flags & UMA_ZFLAG_CACHEONLY)) {
KASSERT((keg->uk_flags & UMA_ZFLAG_OFFPAGE) == 0,
("%s: incompatible flags 0x%b", __func__, keg->uk_flags,
PRINT_UMA_ZFLAGS));
return;
if ((keg->uk_flags &
(UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY)) != 0) {
if (ipers == 0) {
/* We need an extra page for the slab header. */
pages++;
slabsize = ptoa(pages);
ipers = slab_ipers_hdr(keg->uk_size, rsize, slabsize,
true);
}
goto out;
}
/*
* See if using an OFFPAGE slab will limit our waste. Only do
* this if it permits more items per-slab.
* See if using an OFFPAGE slab will improve our efficiency.
* Only do this if we are below our efficiency threshold.
*
* XXX We could try growing slabsize to limit max waste as well.
* Historically this was not done because the VM could not
* efficiently handle contiguous allocations.
*/
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_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, "
"maximum wasted space allowed = %d, "
"calculated ipers = %d, "
"new wasted space = %d\n", keg->uk_name, keg, wastedspace,
slabsize / UMA_MAX_WASTE, keg->uk_ipers,
slabsize - keg->uk_ipers * keg->uk_rsize);
/*
* If we had access to memory to embed a slab header we
* also have a page structure to use vtoslab() instead of
* hash to find slabs. If the zone was explicitly created
* OFFPAGE we can't necessarily touch the memory.
*/
keg->uk_flags |= UMA_ZFLAG_OFFPAGE;
eff = UMA_FRAC_FIXPT(ipers * rsize, slabsize);
ipers_offpage = slab_ipers_hdr(keg->uk_size, rsize, slabsize, false);
eff_offpage = UMA_FRAC_FIXPT(ipers_offpage * rsize,
slabsize + slab_sizeof(SLAB_MAX_SETSIZE));
if (ipers == 0 || (eff < UMA_MIN_EFF && eff < eff_offpage)) {
CTR5(KTR_UMA, "UMA decided we need offpage slab headers for "
"keg: %s(%p), minimum efficiency allowed = %u%%, "
"old efficiency = %u%%, offpage efficiency = %u%%\n",
keg->uk_name, keg, UMA_FIXPT_PCT(UMA_MIN_EFF),
UMA_FIXPT_PCT(eff), UMA_FIXPT_PCT(eff_offpage));
format = UMA_ZFLAG_OFFPAGE;
ipers = ipers_offpage;
}
if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) != 0) {
if ((keg->uk_flags & UMA_ZONE_NOTPAGE) != 0)
keg->uk_flags |= UMA_ZFLAG_HASH;
else
keg->uk_flags |= UMA_ZFLAG_VTOSLAB;
}
}
/*
* Finish creating a large (> UMA_SLAB_SIZE) uma kegs. Just give in and do
* OFFPAGE for now. When I can allow for more dynamic slab sizes this will be
* more complicated.
*
* Arguments
* keg The keg we should initialize
*
* Returns
* Nothing
*/
static void
keg_large_init(uma_keg_t keg)
{
KASSERT(keg != NULL, ("Keg is null in keg_large_init"));
KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
("%s: Cannot large-init a UMA_ZONE_PCPU keg", __func__));
keg->uk_ppera = howmany(keg->uk_size, PAGE_SIZE);
keg->uk_ipers = 1;
keg->uk_rsize = keg->uk_size;
/* Check whether we have enough space to not do OFFPAGE. */
if ((keg->uk_flags & UMA_ZONE_NOTOUCH) == 0 &&
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
* slab header.
*/
if ((keg->uk_flags & UMA_ZFLAG_INTERNAL) == 0)
keg->uk_flags |= UMA_ZFLAG_OFFPAGE;
else
keg->uk_ppera++;
}
if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) != 0) {
if ((keg->uk_flags & UMA_ZONE_NOTPAGE) != 0)
keg->uk_flags |= UMA_ZFLAG_HASH;
else
keg->uk_flags |= UMA_ZFLAG_VTOSLAB;
}
}
static void
keg_cachespread_init(uma_keg_t keg)
{
int alignsize;
int trailer;
int pages;
int rsize;
KASSERT((keg->uk_flags & UMA_ZONE_PCPU) == 0,
("%s: Cannot cachespread-init a UMA_ZONE_PCPU keg", __func__));
alignsize = keg->uk_align + 1;
rsize = keg->uk_size;
out:
/*
* We want one item to start on every align boundary in a page. To
* do this we will span pages. We will also extend the item by the
* size of align if it is an even multiple of align. Otherwise, it
* would fall on the same boundary every time.
* How do we find the slab header if it is offpage or if not all item
* start addresses are in the same page? We could solve the latter
* case with vaddr alignment, but we don't.
*/
if (rsize & keg->uk_align)
rsize = (rsize & ~keg->uk_align) + alignsize;
if ((rsize & alignsize) == 0)
rsize += alignsize;
trailer = rsize - keg->uk_size;
pages = (rsize * (PAGE_SIZE / alignsize)) / PAGE_SIZE;
pages = MIN(pages, (128 * 1024) / PAGE_SIZE);
if ((format & UMA_ZFLAG_OFFPAGE) != 0 ||
(ipers - 1) * rsize >= PAGE_SIZE) {
if ((keg->uk_flags & UMA_ZONE_NOTPAGE) != 0)
format |= UMA_ZFLAG_HASH;
else
format |= UMA_ZFLAG_VTOSLAB;
}
keg->uk_ipers = ipers;
keg->uk_rsize = rsize;
keg->uk_flags |= format;
keg->uk_ppera = pages;
keg->uk_ipers = ((pages * PAGE_SIZE) + trailer) / rsize;
keg->uk_flags |= UMA_ZFLAG_OFFPAGE | UMA_ZFLAG_VTOSLAB;
KASSERT(keg->uk_ipers <= SLAB_MAX_SETSIZE,
("%s: keg->uk_ipers too high(%d) increase max_ipers", __func__,
keg->uk_ipers));
CTR6(KTR_UMA, "%s: keg=%s, flags=%#x, rsize=%u, ipers=%u, ppera=%u\n",
__func__, keg->uk_name, keg->uk_flags, rsize, ipers, pages);
KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_MAX_SETSIZE,
("%s: keg=%s, flags=0x%b, rsize=%u, ipers=%u, ppera=%u", __func__,
keg->uk_name, keg->uk_flags, PRINT_UMA_ZFLAGS, rsize, ipers,
pages));
}
/*
@ -1942,14 +1918,7 @@ keg_ctor(void *mem, int size, void *udata, int flags)
keg->uk_flags &= ~UMA_ZONE_PCPU;
#endif
if (keg->uk_flags & UMA_ZONE_CACHESPREAD) {
keg_cachespread_init(keg);
} else {
if (keg->uk_size > slab_space(SLAB_MIN_SETSIZE))
keg_large_init(keg);
else
keg_small_init(keg);
}
keg_layout(keg);
/*
* Use a first-touch NUMA policy for all kegs that pmap_extract()

3
sys/vm/uma_int.h
View File

@ -139,6 +139,9 @@
/* Max waste percentage before going to off page slab management */
#define UMA_MAX_WASTE 10
/* Max size of a CACHESPREAD slab. */
#define UMA_CACHESPREAD_MAX_SIZE (128 * 1024)
/*
* These flags must not overlap with the UMA_ZONE flags specified in uma.h.
*/