156 lines
3.9 KiB
C
156 lines
3.9 KiB
C
/*
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* mm/thrash.c
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*
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* Copyright (C) 2004, Red Hat, Inc.
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* Copyright (C) 2004, Rik van Riel <riel@redhat.com>
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* Released under the GPL, see the file COPYING for details.
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*
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* Simple token based thrashing protection, using the algorithm
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* described in: http://www.cse.ohio-state.edu/hpcs/WWW/HTML/publications/abs05-1.html
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*
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* Sep 2006, Ashwin Chaugule <ashwin.chaugule@celunite.com>
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* Improved algorithm to pass token:
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* Each task has a priority which is incremented if it contended
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* for the token in an interval less than its previous attempt.
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* If the token is acquired, that task's priority is boosted to prevent
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* the token from bouncing around too often and to let the task make
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* some progress in its execution.
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*/
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#include <linux/jiffies.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/swap.h>
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#include <linux/memcontrol.h>
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#include <trace/events/vmscan.h>
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#define TOKEN_AGING_INTERVAL (0xFF)
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static DEFINE_SPINLOCK(swap_token_lock);
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struct mm_struct *swap_token_mm;
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struct mem_cgroup *swap_token_memcg;
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#ifdef CONFIG_CGROUP_MEM_RES_CTLR
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static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm)
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{
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struct mem_cgroup *memcg;
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memcg = try_get_mem_cgroup_from_mm(mm);
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if (memcg)
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css_put(mem_cgroup_css(memcg));
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return memcg;
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}
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#else
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static struct mem_cgroup *swap_token_memcg_from_mm(struct mm_struct *mm)
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{
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return NULL;
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}
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#endif
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void grab_swap_token(struct mm_struct *mm)
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{
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int current_interval;
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unsigned int old_prio = mm->token_priority;
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static unsigned int global_faults;
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static unsigned int last_aging;
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global_faults++;
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current_interval = global_faults - mm->faultstamp;
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if (!spin_trylock(&swap_token_lock))
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return;
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/* First come first served */
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if (!swap_token_mm)
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goto replace_token;
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/*
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* Usually, we don't need priority aging because long interval faults
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* makes priority decrease quickly. But there is one exception. If the
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* token owner task is sleeping, it never make long interval faults.
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* Thus, we need a priority aging mechanism instead. The requirements
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* of priority aging are
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* 1) An aging interval is reasonable enough long. Too short aging
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* interval makes quick swap token lost and decrease performance.
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* 2) The swap token owner task have to get priority aging even if
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* it's under sleep.
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*/
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if ((global_faults - last_aging) > TOKEN_AGING_INTERVAL) {
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swap_token_mm->token_priority /= 2;
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last_aging = global_faults;
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}
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if (mm == swap_token_mm) {
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mm->token_priority += 2;
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goto update_priority;
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}
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if (current_interval < mm->last_interval)
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mm->token_priority++;
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else {
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if (likely(mm->token_priority > 0))
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mm->token_priority--;
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}
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/* Check if we deserve the token */
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if (mm->token_priority > swap_token_mm->token_priority)
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goto replace_token;
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update_priority:
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trace_update_swap_token_priority(mm, old_prio, swap_token_mm);
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out:
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mm->faultstamp = global_faults;
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mm->last_interval = current_interval;
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spin_unlock(&swap_token_lock);
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return;
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replace_token:
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mm->token_priority += 2;
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trace_replace_swap_token(swap_token_mm, mm);
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swap_token_mm = mm;
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swap_token_memcg = swap_token_memcg_from_mm(mm);
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last_aging = global_faults;
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goto out;
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}
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/* Called on process exit. */
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void __put_swap_token(struct mm_struct *mm)
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{
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spin_lock(&swap_token_lock);
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if (likely(mm == swap_token_mm)) {
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trace_put_swap_token(swap_token_mm);
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swap_token_mm = NULL;
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swap_token_memcg = NULL;
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}
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spin_unlock(&swap_token_lock);
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}
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static bool match_memcg(struct mem_cgroup *a, struct mem_cgroup *b)
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{
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if (!a)
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return true;
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if (!b)
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return true;
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if (a == b)
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return true;
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return false;
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}
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void disable_swap_token(struct mem_cgroup *memcg)
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{
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/* memcg reclaim don't disable unrelated mm token. */
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if (match_memcg(memcg, swap_token_memcg)) {
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spin_lock(&swap_token_lock);
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if (match_memcg(memcg, swap_token_memcg)) {
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trace_disable_swap_token(swap_token_mm);
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swap_token_mm = NULL;
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swap_token_memcg = NULL;
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}
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spin_unlock(&swap_token_lock);
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}
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}
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