d7911ef30c
While testing for memcg aware swap token, I observed a swap token was often grabbed an intermittent running process (eg init, auditd) and they never release a token. Why? Some processes (eg init, auditd, audispd) wake up when a process exiting. And swap token can be get first page-in process when a process exiting makes no swap token owner. Thus such above intermittent running process often get a token. And currently, swap token priority is only decreased at page fault path. Then, if the process sleep immediately after to grab swap token, the swap token priority never be decreased. That's obviously undesirable. This patch implement very poor (and lightweight) priority aging. It only be affect to the above corner case and doesn't change swap tendency workload performance (eg multi process qsbench load) Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
145 lines
3.3 KiB
C
145 lines
3.3 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.cs.wm.edu/~sjiang/token.pdf
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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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static unsigned int global_faults;
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static unsigned int last_aging;
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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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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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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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