Patch series "mm: remove quicklist page table caches". A while ago Nicholas proposed to remove quicklist page table caches [1]. I've rebased his patch on the curren upstream and switched ia64 and sh to use generic versions of PTE allocation. [1] https://lore.kernel.org/linux-mm/20190711030339.20892-1-npiggin@gmail.com This patch (of 3): Remove page table allocator "quicklists". These have been around for a long time, but have not got much traction in the last decade and are only used on ia64 and sh architectures. The numbers in the initial commit look interesting but probably don't apply anymore. If anybody wants to resurrect this it's in the git history, but it's unhelpful to have this code and divergent allocator behaviour for minor archs. Also it might be better to instead make more general improvements to page allocator if this is still so slow.
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| 1 | /* SPDX-License-Identifier: GPL-2.0 */ | ||
| 2 | #ifndef LINUX_QUICKLIST_H | ||
| 3 | #define LINUX_QUICKLIST_H | ||
| 4 | /* | ||
| 5 | * Fast allocations and disposal of pages. Pages must be in the condition | ||
| 6 | * as needed after allocation when they are freed. Per cpu lists of pages | ||
| 7 | * are kept that only contain node local pages. | ||
| 8 | * | ||
| 9 | * (C) 2007, SGI. Christoph Lameter <cl@linux.com> | ||
| 10 | */ | ||
| 11 | #include <linux/kernel.h> | ||
| 12 | #include <linux/gfp.h> | ||
| 13 | #include <linux/percpu.h> | ||
| 14 | |||
| 15 | #ifdef CONFIG_QUICKLIST | ||
| 16 | |||
| 17 | struct quicklist { | ||
| 18 | void *page; | ||
| 19 | int nr_pages; | ||
| 20 | }; | ||
| 21 | |||
| 22 | DECLARE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK]; | ||
| 23 | |||
| 24 | /* | ||
| 25 | * The two key functions quicklist_alloc and quicklist_free are inline so | ||
| 26 | * that they may be custom compiled for the platform. | ||
| 27 | * Specifying a NULL ctor can remove constructor support. Specifying | ||
| 28 | * a constant quicklist allows the determination of the exact address | ||
| 29 | * in the per cpu area. | ||
| 30 | * | ||
| 31 | * The fast patch in quicklist_alloc touched only a per cpu cacheline and | ||
| 32 | * the first cacheline of the page itself. There is minmal overhead involved. | ||
| 33 | */ | ||
| 34 | static inline void *quicklist_alloc(int nr, gfp_t flags, void (*ctor)(void *)) | ||
| 35 | { | ||
| 36 | struct quicklist *q; | ||
| 37 | void **p = NULL; | ||
| 38 | |||
| 39 | q =&get_cpu_var(quicklist)[nr]; | ||
| 40 | p = q->page; | ||
| 41 | if (likely(p)) { | ||
| 42 | q->page = p[0]; | ||
| 43 | p[0] = NULL; | ||
| 44 | q->nr_pages--; | ||
| 45 | } | ||
| 46 | put_cpu_var(quicklist); | ||
| 47 | if (likely(p)) | ||
| 48 | return p; | ||
| 49 | |||
| 50 | p = (void *)__get_free_page(flags | __GFP_ZERO); | ||
| 51 | if (ctor && p) | ||
| 52 | ctor(p); | ||
| 53 | return p; | ||
| 54 | } | ||
| 55 | |||
| 56 | static inline void __quicklist_free(int nr, void (*dtor)(void *), void *p, | ||
| 57 | struct page *page) | ||
| 58 | { | ||
| 59 | struct quicklist *q; | ||
| 60 | |||
| 61 | q = &get_cpu_var(quicklist)[nr]; | ||
| 62 | *(void **)p = q->page; | ||
| 63 | q->page = p; | ||
| 64 | q->nr_pages++; | ||
| 65 | put_cpu_var(quicklist); | ||
| 66 | } | ||
| 67 | |||
| 68 | static inline void quicklist_free(int nr, void (*dtor)(void *), void *pp) | ||
| 69 | { | ||
| 70 | __quicklist_free(nr, dtor, pp, virt_to_page(pp)); | ||
| 71 | } | ||
| 72 | |||
| 73 | static inline void quicklist_free_page(int nr, void (*dtor)(void *), | ||
| 74 | struct page *page) | ||
| 75 | { | ||
| 76 | __quicklist_free(nr, dtor, page_address(page), page); | ||
| 77 | } | ||
| 78 | |||
| 79 | void quicklist_trim(int nr, void (*dtor)(void *), | ||
| 80 | unsigned long min_pages, unsigned long max_free); | ||
| 81 | |||
| 82 | unsigned long quicklist_total_size(void); | ||
| 83 | |||
| 84 | #else | ||
| 85 | |||
| 86 | static inline unsigned long quicklist_total_size(void) | ||
| 87 | { | ||
| 88 | return 0; | ||
| 89 | } | ||
| 90 | |||
| 91 | #endif | ||
| 92 | |||
| 93 | #endif /* LINUX_QUICKLIST_H */ | ||
| 94 | |||