d27f29b468
Refactor arena and extent locking protocols such that arena and
extent locks are never held when calling into the extent_*_wrapper()
API. This requires extra care during purging since the arena lock no
longer protects the inner purging logic. It also requires extra care to
protect extents from being merged with adjacent extents.
Convert extent_t's 'active' flag to an enumerated 'state', so that
retained extents are explicitly marked as such, rather than depending on
ring linkage state.
Refactor the extent collections (and their synchronization) for cached
and retained extents into extents_t. Incorporate LRU functionality to
support purging. Incorporate page count accounting, which replaces
arena->ndirty and arena->stats.retained.
Assert that no core locks are held when entering any internal
[de]allocation functions. This is in addition to existing assertions
that no locks are held when entering external [de]allocation functions.
Audit and document synchronization protocols for all arena_t fields.
This fixes a potential deadlock due to recursive allocation during
gdump, in a similar fashion to b49c649bc1
(Fix lock order reversal during gdump.), but with a necessarily much
broader code impact.
121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
#ifndef JEMALLOC_INTERNAL_EXTENT_STRUCTS_H
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#define JEMALLOC_INTERNAL_EXTENT_STRUCTS_H
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typedef enum {
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extent_state_active = 0,
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extent_state_dirty = 1,
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extent_state_retained = 2
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} extent_state_t;
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/* Extent (span of pages). Use accessor functions for e_* fields. */
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struct extent_s {
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/* Arena from which this extent came, if any. */
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arena_t *e_arena;
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/* Pointer to the extent that this structure is responsible for. */
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void *e_addr;
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/* Extent size. */
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size_t e_size;
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/*
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* Usable size, typically smaller than extent size due to large_pad or
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* promotion of sampled small regions.
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*/
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size_t e_usize;
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/*
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* Serial number (potentially non-unique).
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*
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* In principle serial numbers can wrap around on 32-bit systems if
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* JEMALLOC_MUNMAP is defined, but as long as comparison functions fall
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* back on address comparison for equal serial numbers, stable (if
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* imperfect) ordering is maintained.
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*
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* Serial numbers may not be unique even in the absence of wrap-around,
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* e.g. when splitting an extent and assigning the same serial number to
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* both resulting adjacent extents.
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*/
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size_t e_sn;
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/* Extent state. */
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extent_state_t e_state;
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/*
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* The zeroed flag is used by extent recycling code to track whether
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* memory is zero-filled.
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*/
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bool e_zeroed;
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/*
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* True if physical memory is committed to the extent, whether
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* explicitly or implicitly as on a system that overcommits and
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* satisfies physical memory needs on demand via soft page faults.
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*/
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bool e_committed;
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/*
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* The slab flag indicates whether the extent is used for a slab of
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* small regions. This helps differentiate small size classes, and it
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* indicates whether interior pointers can be looked up via iealloc().
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*/
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bool e_slab;
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union {
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/* Small region slab metadata. */
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arena_slab_data_t e_slab_data;
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/* Profile counters, used for large objects. */
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union {
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void *e_prof_tctx_pun;
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prof_tctx_t *e_prof_tctx;
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};
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};
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/*
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* List linkage, used by a variety of lists:
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* - arena_bin_t's slabs_full
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* - extents_t's LRU
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* - stashed dirty extents
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* - arena's large allocations
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* - arena's extent structure freelist
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*/
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ql_elm(extent_t) ql_link;
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/* Linkage for per size class sn/address-ordered heaps. */
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phn(extent_t) ph_link;
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};
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typedef ql_head(extent_t) extent_list_t;
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typedef ph(extent_t) extent_heap_t;
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/* Quantized collection of extents, with built-in LRU queue. */
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struct extents_s {
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malloc_mutex_t mtx;
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/*
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* Quantized per size class heaps of extents.
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*
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* Synchronization: mtx.
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*/
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extent_heap_t heaps[NPSIZES+1];
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/*
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* LRU of all extents in heaps.
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*
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* Synchronization: mtx.
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*/
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extent_list_t lru;
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/*
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* Page sum for all extents in heaps.
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*
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* Synchronization: atomic.
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*/
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size_t npages;
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/* All stored extents must be in the same state. */
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extent_state_t state;
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};
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#endif /* JEMALLOC_INTERNAL_EXTENT_STRUCTS_H */
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