Topics Not Covered. Debugging (includes kmemcheck, kmemleak) Statistics Tracing UP UMA CPU and Memory Hotplug Lockdep Failslab

Transcription

1 Topics Not Covered Debugging (includes kmemcheck, kmemleak) Statistics Tracing UP UMA CPU and Memory Hotplug Lockdep Failslab

2 SLAB Allocates from per-cpu array with interrupts disabled Fallsback to nodelist's shared array (shared by all local nodes) Otherwise, search node's partial list with centralized locking Periodically drains free objects back to slabs and free slabs back to page allocator

3 SLAB Fallsback to allocating new slab from page allocator Specializes in low-order slab pages, easy to allocate Scales exponentially with many cpus and nodes with alien caches Per-object mempolicy and cpuset support

4 SLUB Unqueued slab allocator, developed for large systems Performance improves with higher order slabs Relies heavily on cmpxchg_double(), limited hardware support Fallsback to disabling interrupts in the fastpaths

5 SLUB Recently introduced per-cpu partial lists Fallsback to per-node partial lists with centralized locking Merges caches with the same characteristics together No per-object mempolicy or cpuset support

6 Bucket sizes... kmalloc 256 kmalloc 512 kmalloc 1024 kmalloc

7 struct kmem_cache_objects Represents a list of free objects. unsigned long void void avail **head **tail

8 struct kmem_cache_slabs Represents a local, remote, and a list of partial slabs. struct kmem_cache_objects struct kmem_cache_objects spinlock_t bool unsigned long struct list_head struct kmem_cache remote_ lock remote_free_check nr_partial partial *cache

9 struct kmem_cache_cpu Represents a local cpu slab and list of objects freed remotely. struct kmem_cache_slabs struct kmem_cache_objects remote_objects struct kmem_cache_slabs *remote_slab_list

10 struct kmem_cache_node Represents a local, remote, and a list of partial slabs protected by a spinlock. struct kmem_cache_slabs spinlock_t slab_list

11 SLAM: A Mutable Slab Allocation System The Allocation Fastpath...

12 cpu void void **head **head

13 kmalloc(256) 256 bytes cpu void void **head **head

14 kmalloc(256, SLAB_TEMPORARY) 256 bytes cpu 512 bytes avail avail == 00 void void **head **head

15 cpu remote_free_check remote_free_check == true true remote_ remote_ avail avail >> 00 void void **head **head remote_free_check remote_free_check == false false

16 cpu nr_partial nr_partial >> 00 partial partial avail avail >> 00 void void **head **head nr_partial-nr_partial- head head == partial->head partial->head

17 And the Slowpath...

18 Page allocator cpu Local Page partial partial nr_partials++ nr_partials++ avail avail == 00 if GFP_WAIT

19 Page allocator cpu Remote Page partial partial nr_partials nr_partials == 00 node slab_list slab_list if GFP_WAIT avail avail == 00

20 node slab_list slab_list void void **head **head

21 node slab_list slab_list remote_free_check remote_free_check == true true remote_ remote_ avail avail >> 00 void void **head **head remote_free_check remote_free_check == false false

22 node slab_list slab_list nr_partial nr_partial >> 00 partial partial avail avail >> 00 void void **head **head nr_partial-nr_partial- head head == partial->head partial->head

23 Page allocator node slab_list slab_list Remote Page partial partial nr_partials nr_partials == 00 avail avail == 00

24 The Free Fastpath...

25 cpu obj obj ++ offset offset == head head head head == obj obj avail++ avail++ LIFO

26 void **head void **tail obj obj obj obj obj obj obj obj obj obj obj batchcount

27 void **head void **tail obj obj obj obj obj obj obj batchcount obj obj obj obj Local Page inuse-- Local Page inuse - 3

28 void **head void **tail obj obj obj obj obj obj obj batchcount obj obj obj obj Local Page Local Page inuse = objects + 1 nr_partial++ nr_partial++ partial partial

29 void **head void **tail obj obj obj obj obj obj obj batchcount obj obj obj obj Local Page Local Page inuse = 0 nr_partial-nr_partial-partial partial Page allocator

30 void **head void **tail obj obj obj obj obj obj obj batchcount obj obj obj obj Local Page Remote Page inuse = 0 nr_partial nr_partial == 00 partial partial Page allocator

31 cpu *remote_slab_list *remote_slab_list remote_objects remote_objects obj Remote Page ->list obj obj ++ offset offset == head head head head == obj obj avail++ avail++ LIFO

32 cpu *remote_slab_list *remote_slab_list remote_objects remote_objects obj void void **head **head Remote Page ->list lock lock lock remote_ remote_ remote_free_check remote_free_check == true true

33 cpu *remote_slab_list *remote_slab_list remote_objects remote_objects obj head head == NULL NULL avail avail == 00 Remote Page ->list