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c721ce1a3f
For each lruvec, evictable pages are divided into multiple generations. The youngest generation number is stored in lrugen->max_seq for both anon and file types as they are aged on an equal footing. The oldest generation numbers are stored in lrugen->min_seq[2] separately for anon and file types as clean file pages can be evicted regardless of may_swap or may_writepage. These three variables are monotonically increasing. Generation numbers are truncated into order_base_2(MAX_NR_GENS+1) bits in order to fit into page->flags. The sliding window technique is used to prevent truncated generation numbers from overlapping. Each truncated generation number is an index to lrugen->lists[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]. Evictable pages are added to the per-zone lists indexed by lrugen->max_seq or lrugen->min_seq[2] (modulo MAX_NR_GENS), depending on their types. Each generation is then divided into multiple tiers. Tiers represent levels of usage from file descriptors only. Pages accessed N times via file descriptors belong to tier order_base_2(N). Each generation contains at most MAX_NR_TIERS tiers, and they require additional MAX_NR_TIERS-2 bits in page->flags. In contrast to moving across generations which requires the lru lock for the list operations, moving across tiers only involves an atomic operation on page->flags and therefore has a negligible cost. A feedback loop modeled after the PID controller monitors the refault rates across all tiers and decides when to activate pages from which tiers in the reclaim path. The framework comprises two conceptually independent components: the aging and the eviction, which can be invoked separately from user space for the purpose of working set estimation and proactive reclaim. The aging produces young generations. Given an lruvec, the aging scans page tables for referenced pages of this lruvec. Upon finding one, the aging updates its generation number to max_seq. After each round of scan, the aging increments max_seq. The aging is due when both of min_seq[2] reaches max_seq-1, assuming both anon and file types are reclaimable. The eviction consumes old generations. Given an lruvec, the eviction scans the pages on the per-zone lists indexed by either of min_seq[2]. It tries to select a type based on the values of min_seq[2] and swappiness. During a scan, the eviction sorts pages according to their new generation numbers, if the aging has found them referenced. When it finds all the per-zone lists of a selected type are empty, the eviction increments min_seq[2] indexed by this selected type. Signed-off-by: Yu Zhao <yuzhao@google.com> Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru> (am from https://lore.kernel.org/patchwork/patch/1432182/) BUG=b:123039911 TEST=Built Change-Id: I71de7cd15b8dfa6f9fdd838023474693c4fee0a7 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2928251 Reviewed-by: Yu Zhao <yuzhao@chromium.org> Reviewed-by: Sonny Rao <sonnyrao@chromium.org> Tested-by: Yu Zhao <yuzhao@chromium.org> Commit-Queue: Yu Zhao <yuzhao@chromium.org> Signed-off-by: azrim <mirzaspc@gmail.com>
35 lines
1.0 KiB
C
35 lines
1.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Generate definitions needed by the preprocessor.
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* This code generates raw asm output which is post-processed
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* to extract and format the required data.
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*/
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#define __GENERATING_BOUNDS_H
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/* Include headers that define the enum constants of interest */
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#include <linux/page-flags.h>
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#include <linux/mmzone.h>
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#include <linux/kbuild.h>
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#include <linux/log2.h>
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#include <linux/spinlock_types.h>
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int main(void)
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{
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/* The enum constants to put into include/generated/bounds.h */
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DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
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DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES);
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#ifdef CONFIG_SMP
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DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
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#endif
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DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
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#ifdef CONFIG_LRU_GEN
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/* bits needed to represent internal values stored in page->flags */
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DEFINE(LRU_GEN_WIDTH, order_base_2(CONFIG_NR_LRU_GENS + 1));
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/* bits needed to represent normalized values for external uses */
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DEFINE(LRU_GEN_SHIFT, order_base_2(CONFIG_NR_LRU_GENS));
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#endif
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/* End of constants */
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return 0;
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}
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