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performance. - Always free to the alloc bucket if there is space. This gives LIFO allocation order to improve hot-cache performance. This also allows for zones with a single bucket per-cpu rather than a pair if the entire working set fits in one bucket. - Enable per-cpu caches of buckets. To prevent recursive bucket allocation one bucket zone still has per-cpu caches disabled. - Pick the initial bucket size based on a table driven maximum size per-bucket rather than the number of items per-page. This gives more sane initial sizes. - Only grow the bucket size when we face contention on the zone lock, this causes bucket sizes to grow more slowly. - Adjust the number of items per-bucket to account for the header space. This packs the buckets more efficiently per-page while making them not quite powers of two. - Eliminate the per-zone free bucket list. Always return buckets back to the bucket zone. This ensures that as zones grow into larger bucket sizes they eventually discard the smaller sizes. It persists fewer buckets in the system. The locking is slightly trickier. - Only switch buckets in zalloc, not zfree, this eliminates pathological cases where we ping-pong between two buckets. - Ensure that the thread that fills a new bucket gets to allocate from it to give a better upper bound on allocation time. Sponsored by: EMC / Isilon Storage Division
439 lines
15 KiB
C
439 lines
15 KiB
C
/*-
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* Copyright (c) 2002-2005, 2009, 2013 Jeffrey Roberson <jeff@FreeBSD.org>
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* Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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*/
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/*
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* This file includes definitions, structures, prototypes, and inlines that
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* should not be used outside of the actual implementation of UMA.
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*/
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/*
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* Here's a quick description of the relationship between the objects:
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*
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* Kegs contain lists of slabs which are stored in either the full bin, empty
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* bin, or partially allocated bin, to reduce fragmentation. They also contain
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* the user supplied value for size, which is adjusted for alignment purposes
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* and rsize is the result of that. The Keg also stores information for
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* managing a hash of page addresses that maps pages to uma_slab_t structures
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* for pages that don't have embedded uma_slab_t's.
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*
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* The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
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* be allocated off the page from a special slab zone. The free list within a
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* slab is managed with a bitmask. For item sizes that would yield more than
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* 10% memory waste we potentially allocate a separate uma_slab_t if this will
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* improve the number of items per slab that will fit.
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*
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* Other potential space optimizations are storing the 8bit of linkage in space
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* wasted between items due to alignment problems. This may yield a much better
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* memory footprint for certain sizes of objects. Another alternative is to
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* increase the UMA_SLAB_SIZE, or allow for dynamic slab sizes. I prefer
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* dynamic slab sizes because we could stick with 8 bit indices and only use
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* large slab sizes for zones with a lot of waste per slab. This may create
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* inefficiencies in the vm subsystem due to fragmentation in the address space.
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*
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* The only really gross cases, with regards to memory waste, are for those
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* items that are just over half the page size. You can get nearly 50% waste,
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* so you fall back to the memory footprint of the power of two allocator. I
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* have looked at memory allocation sizes on many of the machines available to
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* me, and there does not seem to be an abundance of allocations at this range
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* so at this time it may not make sense to optimize for it. This can, of
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* course, be solved with dynamic slab sizes.
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*
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* Kegs may serve multiple Zones but by far most of the time they only serve
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* one. When a Zone is created, a Keg is allocated and setup for it. While
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* the backing Keg stores slabs, the Zone caches Buckets of items allocated
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* from the slabs. Each Zone is equipped with an init/fini and ctor/dtor
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* pair, as well as with its own set of small per-CPU caches, layered above
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* the Zone's general Bucket cache.
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*
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* The PCPU caches are protected by critical sections, and may be accessed
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* safely only from their associated CPU, while the Zones backed by the same
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* Keg all share a common Keg lock (to coalesce contention on the backing
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* slabs). The backing Keg typically only serves one Zone but in the case of
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* multiple Zones, one of the Zones is considered the Master Zone and all
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* Zone-related stats from the Keg are done in the Master Zone. For an
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* example of a Multi-Zone setup, refer to the Mbuf allocation code.
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*/
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/*
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* This is the representation for normal (Non OFFPAGE slab)
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*
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* i == item
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* s == slab pointer
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*
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* <---------------- Page (UMA_SLAB_SIZE) ------------------>
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* ___________________________________________________________
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* | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___________ |
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* ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
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* ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________||
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* |___________________________________________________________|
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*
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*
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* This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
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*
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* ___________________________________________________________
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* | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ |
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* ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |
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* ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |
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* |___________________________________________________________|
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* ___________ ^
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* |slab header| |
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* |___________|---*
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*
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*/
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#ifndef VM_UMA_INT_H
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#define VM_UMA_INT_H
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#define UMA_SLAB_SIZE PAGE_SIZE /* How big are our slabs? */
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#define UMA_SLAB_MASK (PAGE_SIZE - 1) /* Mask to get back to the page */
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#define UMA_SLAB_SHIFT PAGE_SHIFT /* Number of bits PAGE_MASK */
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#define UMA_BOOT_PAGES 64 /* Pages allocated for startup */
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/* Max waste percentage before going to off page slab management */
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#define UMA_MAX_WASTE 10
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/*
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* I doubt there will be many cases where this is exceeded. This is the initial
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* size of the hash table for uma_slabs that are managed off page. This hash
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* does expand by powers of two. Currently it doesn't get smaller.
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*/
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#define UMA_HASH_SIZE_INIT 32
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/*
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* I should investigate other hashing algorithms. This should yield a low
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* number of collisions if the pages are relatively contiguous.
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*/
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#define UMA_HASH(h, s) ((((uintptr_t)s) >> UMA_SLAB_SHIFT) & (h)->uh_hashmask)
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#define UMA_HASH_INSERT(h, s, mem) \
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SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h), \
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(mem))], (s), us_hlink)
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#define UMA_HASH_REMOVE(h, s, mem) \
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SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h), \
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(mem))], (s), uma_slab, us_hlink)
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/* Hash table for freed address -> slab translation */
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SLIST_HEAD(slabhead, uma_slab);
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struct uma_hash {
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struct slabhead *uh_slab_hash; /* Hash table for slabs */
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int uh_hashsize; /* Current size of the hash table */
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int uh_hashmask; /* Mask used during hashing */
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};
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/*
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* align field or structure to cache line
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*/
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#if defined(__amd64__)
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#define UMA_ALIGN __aligned(CACHE_LINE_SIZE)
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#else
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#define UMA_ALIGN
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#endif
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/*
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* Structures for per cpu queues.
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*/
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struct uma_bucket {
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LIST_ENTRY(uma_bucket) ub_link; /* Link into the zone */
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int16_t ub_cnt; /* Count of free items. */
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int16_t ub_entries; /* Max items. */
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void *ub_bucket[]; /* actual allocation storage */
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};
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typedef struct uma_bucket * uma_bucket_t;
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struct uma_cache {
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uma_bucket_t uc_freebucket; /* Bucket we're freeing to */
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uma_bucket_t uc_allocbucket; /* Bucket to allocate from */
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uint64_t uc_allocs; /* Count of allocations */
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uint64_t uc_frees; /* Count of frees */
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} UMA_ALIGN;
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typedef struct uma_cache * uma_cache_t;
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/*
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* Keg management structure
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*
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* TODO: Optimize for cache line size
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*
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*/
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struct uma_keg {
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struct mtx uk_lock; /* Lock for the keg */
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struct uma_hash uk_hash;
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LIST_HEAD(,uma_zone) uk_zones; /* Keg's zones */
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LIST_HEAD(,uma_slab) uk_part_slab; /* partially allocated slabs */
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LIST_HEAD(,uma_slab) uk_free_slab; /* empty slab list */
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LIST_HEAD(,uma_slab) uk_full_slab; /* full slabs */
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uint32_t uk_align; /* Alignment mask */
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uint32_t uk_pages; /* Total page count */
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uint32_t uk_free; /* Count of items free in slabs */
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uint32_t uk_size; /* Requested size of each item */
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uint32_t uk_rsize; /* Real size of each item */
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uint32_t uk_maxpages; /* Maximum number of pages to alloc */
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uma_init uk_init; /* Keg's init routine */
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uma_fini uk_fini; /* Keg's fini routine */
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uma_alloc uk_allocf; /* Allocation function */
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uma_free uk_freef; /* Free routine */
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u_long uk_offset; /* Next free offset from base KVA */
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vm_offset_t uk_kva; /* Zone base KVA */
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uma_zone_t uk_slabzone; /* Slab zone backing us, if OFFPAGE */
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uint16_t uk_slabsize; /* Slab size for this keg */
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uint16_t uk_pgoff; /* Offset to uma_slab struct */
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uint16_t uk_ppera; /* pages per allocation from backend */
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uint16_t uk_ipers; /* Items per slab */
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uint32_t uk_flags; /* Internal flags */
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/* Least used fields go to the last cache line. */
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const char *uk_name; /* Name of creating zone. */
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LIST_ENTRY(uma_keg) uk_link; /* List of all kegs */
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};
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typedef struct uma_keg * uma_keg_t;
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/*
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* Free bits per-slab.
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*/
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#define SLAB_SETSIZE (PAGE_SIZE / UMA_SMALLEST_UNIT)
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BITSET_DEFINE(slabbits, SLAB_SETSIZE);
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/*
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* The slab structure manages a single contiguous allocation from backing
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* store and subdivides it into individually allocatable items.
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*/
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struct uma_slab {
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uma_keg_t us_keg; /* Keg we live in */
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union {
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LIST_ENTRY(uma_slab) _us_link; /* slabs in zone */
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unsigned long _us_size; /* Size of allocation */
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} us_type;
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SLIST_ENTRY(uma_slab) us_hlink; /* Link for hash table */
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uint8_t *us_data; /* First item */
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struct slabbits us_free; /* Free bitmask. */
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#ifdef INVARIANTS
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struct slabbits us_debugfree; /* Debug bitmask. */
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#endif
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uint16_t us_freecount; /* How many are free? */
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uint8_t us_flags; /* Page flags see uma.h */
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uint8_t us_pad; /* Pad to 32bits, unused. */
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};
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#define us_link us_type._us_link
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#define us_size us_type._us_size
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/*
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* The slab structure for UMA_ZONE_REFCNT zones for whose items we
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* maintain reference counters in the slab for.
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*/
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struct uma_slab_refcnt {
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struct uma_slab us_head; /* slab header data */
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uint32_t us_refcnt[0]; /* Actually larger. */
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};
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typedef struct uma_slab * uma_slab_t;
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typedef struct uma_slab_refcnt * uma_slabrefcnt_t;
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typedef uma_slab_t (*uma_slaballoc)(uma_zone_t, uma_keg_t, int);
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struct uma_klink {
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LIST_ENTRY(uma_klink) kl_link;
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uma_keg_t kl_keg;
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};
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typedef struct uma_klink *uma_klink_t;
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/*
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* Zone management structure
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*
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* TODO: Optimize for cache line size
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*
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*/
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struct uma_zone {
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const char *uz_name; /* Text name of the zone */
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struct mtx *uz_lock; /* Lock for the zone (keg's lock) */
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LIST_ENTRY(uma_zone) uz_link; /* List of all zones in keg */
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LIST_HEAD(,uma_bucket) uz_buckets; /* full buckets */
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LIST_HEAD(,uma_klink) uz_kegs; /* List of kegs. */
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struct uma_klink uz_klink; /* klink for first keg. */
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uma_slaballoc uz_slab; /* Allocate a slab from the backend. */
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uma_ctor uz_ctor; /* Constructor for each allocation */
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uma_dtor uz_dtor; /* Destructor */
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uma_init uz_init; /* Initializer for each item */
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uma_fini uz_fini; /* Finalizer for each item. */
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uma_import uz_import; /* Import new memory to cache. */
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uma_release uz_release; /* Release memory from cache. */
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void *uz_arg; /* Import/release argument. */
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uint32_t uz_flags; /* Flags inherited from kegs */
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uint32_t uz_size; /* Size inherited from kegs */
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volatile u_long uz_allocs UMA_ALIGN; /* Total number of allocations */
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volatile u_long uz_fails; /* Total number of alloc failures */
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volatile u_long uz_frees; /* Total number of frees */
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uint64_t uz_sleeps; /* Total number of alloc sleeps */
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uint16_t uz_count; /* Highest amount of items in bucket */
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/* The next three fields are used to print a rate-limited warnings. */
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const char *uz_warning; /* Warning to print on failure */
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struct timeval uz_ratecheck; /* Warnings rate-limiting */
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/*
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* This HAS to be the last item because we adjust the zone size
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* based on NCPU and then allocate the space for the zones.
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*/
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struct uma_cache uz_cpu[1]; /* Per cpu caches */
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};
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/*
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* These flags must not overlap with the UMA_ZONE flags specified in uma.h.
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*/
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#define UMA_ZFLAG_MULTI 0x04000000 /* Multiple kegs in the zone. */
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#define UMA_ZFLAG_DRAINING 0x08000000 /* Running zone_drain. */
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#define UMA_ZFLAG_PRIVALLOC 0x10000000 /* Use uz_allocf. */
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#define UMA_ZFLAG_INTERNAL 0x20000000 /* No offpage no PCPU. */
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#define UMA_ZFLAG_FULL 0x40000000 /* Reached uz_maxpages */
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#define UMA_ZFLAG_CACHEONLY 0x80000000 /* Don't ask VM for buckets. */
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#define UMA_ZFLAG_INHERIT (UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY)
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static inline uma_keg_t
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zone_first_keg(uma_zone_t zone)
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{
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return (LIST_FIRST(&zone->uz_kegs)->kl_keg);
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}
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#undef UMA_ALIGN
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#ifdef _KERNEL
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/* Internal prototypes */
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static __inline uma_slab_t hash_sfind(struct uma_hash *hash, uint8_t *data);
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void *uma_large_malloc(int size, int wait);
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void uma_large_free(uma_slab_t slab);
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/* Lock Macros */
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#define KEG_LOCK_INIT(k, lc) \
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do { \
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if ((lc)) \
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mtx_init(&(k)->uk_lock, (k)->uk_name, \
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(k)->uk_name, MTX_DEF | MTX_DUPOK); \
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else \
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mtx_init(&(k)->uk_lock, (k)->uk_name, \
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"UMA zone", MTX_DEF | MTX_DUPOK); \
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} while (0)
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#define KEG_LOCK_FINI(k) mtx_destroy(&(k)->uk_lock)
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#define KEG_LOCK(k) mtx_lock(&(k)->uk_lock)
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#define KEG_UNLOCK(k) mtx_unlock(&(k)->uk_lock)
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#define ZONE_LOCK(z) mtx_lock((z)->uz_lock)
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#define ZONE_TRYLOCK(z) mtx_trylock((z)->uz_lock)
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#define ZONE_UNLOCK(z) mtx_unlock((z)->uz_lock)
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/*
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* Find a slab within a hash table. This is used for OFFPAGE zones to lookup
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* the slab structure.
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*
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* Arguments:
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* hash The hash table to search.
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* data The base page of the item.
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*
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* Returns:
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* A pointer to a slab if successful, else NULL.
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*/
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static __inline uma_slab_t
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hash_sfind(struct uma_hash *hash, uint8_t *data)
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{
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uma_slab_t slab;
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int hval;
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hval = UMA_HASH(hash, data);
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SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
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if ((uint8_t *)slab->us_data == data)
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return (slab);
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}
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return (NULL);
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}
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static __inline uma_slab_t
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vtoslab(vm_offset_t va)
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{
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vm_page_t p;
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uma_slab_t slab;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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slab = (uma_slab_t )p->object;
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if (p->flags & PG_SLAB)
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return (slab);
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else
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return (NULL);
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}
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static __inline void
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vsetslab(vm_offset_t va, uma_slab_t slab)
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{
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vm_page_t p;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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p->object = (vm_object_t)slab;
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p->flags |= PG_SLAB;
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}
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static __inline void
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vsetobj(vm_offset_t va, vm_object_t obj)
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{
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vm_page_t p;
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p = PHYS_TO_VM_PAGE(pmap_kextract(va));
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p->object = obj;
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p->flags &= ~PG_SLAB;
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}
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/*
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* The following two functions may be defined by architecture specific code
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* if they can provide more effecient allocation functions. This is useful
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* for using direct mapped addresses.
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*/
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void *uma_small_alloc(uma_zone_t zone, int bytes, uint8_t *pflag, int wait);
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void uma_small_free(void *mem, int size, uint8_t flags);
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#endif /* _KERNEL */
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#endif /* VM_UMA_INT_H */
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