Revert "demand_paging: add NRU algorithm"
This reverts commit 200ea42437.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
This commit is contained in:
Anas Nashif
parent
cadb201d1e
commit
4f15aae65a
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@ -1,14 +1,2 @@
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# Copyright (c) 2020 Intel Corporation
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# Copyright (c) 2020 Intel Corporation
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# SPDX-License-Identifier: Apache-2.0
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# SPDX-License-Identifier: Apache-2.0
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add_definitions(-D__ZEPHYR_SUPERVISOR__)
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include_directories(
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${ZEPHYR_BASE}/kernel/include
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${ARCH_DIR}/${ARCH}/include
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)
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if(NOT DEFINED CONFIG_EVICTION_CUSTOM)
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zephyr_library()
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zephyr_library_sources_ifdef(CONFIG_EVICTION_NRU nru.c)
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endif()
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@ -5,7 +5,7 @@
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choice EVICTION_CHOICE
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choice EVICTION_CHOICE
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prompt "Page frame eviction algorithms"
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prompt "Page frame eviction algorithms"
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default EVICTION_NRU
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default EVICTION_CUSTOM
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depends on DEMAND_PAGING
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depends on DEMAND_PAGING
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config EVICTION_CUSTOM
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config EVICTION_CUSTOM
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@ -14,27 +14,4 @@ config EVICTION_CUSTOM
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This option is chosen when the eviction algorithm will be implemented
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This option is chosen when the eviction algorithm will be implemented
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by the application, instead of using one included in Zephyr.
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by the application, instead of using one included in Zephyr.
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config EVICTION_NRU
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bool "Not Recently Used (NRU) page eviction algorithm"
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help
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This implements a Not Recently Used page eviction algorithm.
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A periodic timer will clear the accessed state of all virtual pages.
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When a page frame needs to be evicted, the algorithm will prefer to
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evict page frames using an ascending order of priority:
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- recently accessed, dirty
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- recently accessed, clean
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- not recently accessed, dirty
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- not recently accessed, clean
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endchoice
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endchoice
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if EVICTION_NRU
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config EVICTION_NRU_PERIOD
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int "Recently accessed period, in milliseconds"
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default 100
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help
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A periodic timer will fire that clears the accessed state of all virtual
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pages that are capable of being paged out. At eviction time, if a page
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still has the accessed property, it will be considered as recently used.
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endif # EVICTION_NRU
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@ -1,96 +0,0 @@
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/*
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* Copyright (c) 2020 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Not Recently Used (NRU) eviction algorithm for demand paging
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*/
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#include <kernel.h>
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#include <mmu.h>
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#include <kernel_arch_interface.h>
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#include <init.h>
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/* The accessed and dirty states of each page frame are used to create
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* a hierarchy with a numerical value. When evicting a page, try to evict
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* page with the highest value (we prefer clean, not accessed pages).
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*
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* In this ontology, "accessed" means "recently accessed" and gets cleared
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* during the periodic update.
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*
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* 0 not accessed, clean
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* 1 not accessed, dirty
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* 2 accessed, clean
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* 3 accessed, dirty
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*/
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static void nru_periodic_update(struct k_timer *timer)
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{
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uintptr_t phys;
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struct z_page_frame *pf;
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int key = irq_lock();
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Z_PAGE_FRAME_FOREACH(phys, pf) {
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if (!z_page_frame_is_evictable(pf)) {
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continue;
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}
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/* Clear accessed bit in page tables */
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(void)arch_page_info_get(pf->addr, NULL, true);
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}
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irq_unlock(key);
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}
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struct z_page_frame *z_eviction_select(bool *dirty_ptr)
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{
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unsigned int last_prec = 4U;
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struct z_page_frame *last_pf = NULL, *pf;
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bool accessed;
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bool dirty = false;
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uintptr_t flags, phys;
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Z_PAGE_FRAME_FOREACH(phys, pf) {
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unsigned int prec;
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if (!z_page_frame_is_evictable(pf)) {
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continue;
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}
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flags = arch_page_info_get(pf->addr, NULL, false);
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accessed = (flags & ARCH_DATA_PAGE_ACCESSED) != 0UL;
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dirty = (flags & ARCH_DATA_PAGE_DIRTY) != 0UL;
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/* Implies a mismatch with page frame ontology and page
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* tables
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*/
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__ASSERT((flags & ARCH_DATA_PAGE_LOADED) != 0U,
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"non-present page, %s",
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((flags & ARCH_DATA_PAGE_NOT_MAPPED) != 0U) ?
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"un-mapped" : "paged out");
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prec = (dirty ? 1U : 0U) + (accessed ? 2U : 0U);
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if (prec == 0) {
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/* If we find a not accessed, clean page we're done */
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last_pf = pf;
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break;
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}
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if (prec < last_prec) {
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last_prec = prec;
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last_pf = pf;
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}
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}
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/* Shouldn't ever happen unless every page is pinned */
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__ASSERT(last_pf != NULL, "no page to evict");
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*dirty_ptr = dirty;
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return last_pf;
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}
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static K_TIMER_DEFINE(nru_timer, nru_periodic_update, NULL);
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void z_eviction_init(void)
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{
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k_timer_start(&nru_timer, K_NO_WAIT,
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K_MSEC(CONFIG_EVICTION_NRU_PERIOD));
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}
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