Re: [PATCH] token based thrashing control

[jhigdon]

On Fri, Jul 30, 2004 at 05:37:18PM -0400, Rik van Riel wrote:
> 	
> The following experimental patch implements token based thrashing
> protection, using the algorithm described in:
> 
> 	http://www.cs.wm.edu/~sjiang/token.htm
> 
> When there are pageins going on, a task can grab a token, that
> protects the task from pageout (except by itself) until it is
> no longer doing heavy pageins, or until the maximum hold time
> of the token is over.
> 
> If the maximum hold time is exceeded, the task isn't eligable
> to hold the token for a while more, since it wasn't doing it
> much good anyway.
> 
> I have run a very unscientific benchmark on my system to test
> the effectiveness of the patch, timing how a 230MB two-process
> qsbench run takes, with and without the token thrashing
> protection present.
> 
> normal 2.6.8-rc6:	6m45s
> 2.6.8-rc6 + token:	4m24s
> 
> This is a quick hack, implemented without having talked to the
> inventor of the algorithm.  He's copied on the mail and I suspect
> we'll be able to do better than my quick implementation ...
> 
> Please test this patch.

Hello,

I tested this patch on my laptop which is a p2 400 and 128mb of ram.
After loading many applications far more then I usually do (fc2 running gnome2)
the application I currently use tends to be better responsiveness wise. 


> 
>  include/linux/sched.h |    4 ++
>  include/linux/swap.h  |   21 ++++++++++
>  kernel/fork.c         |    2 +
>  mm/Makefile           |    2 -
>  mm/filemap.c          |    1 
>  mm/memory.c           |    1 
>  mm/rmap.c             |    3 +
>  mm/thrash.c           |  100 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  8 files changed, 133 insertions(+), 1 deletion(-)
> 
> --- linux-2.6.7/include/linux/swap.h.token	2004-07-30 13:22:17.000000000 -0400
> +++ linux-2.6.7/include/linux/swap.h	2004-07-30 16:39:27.000000000 -0400
> @@ -204,6 +204,27 @@
>  extern struct page * lookup_swap_cache(swp_entry_t);
>  extern struct page * read_swap_cache_async(swp_entry_t, struct vm_area_struct *vma,
>  					   unsigned long addr);
> +/* linux/mm/thrash.c */
> +#ifdef CONFIG_SWAP
> +extern struct mm_struct * swap_token_mm;
> +extern void grab_swap_token(void);
> +extern void __put_swap_token(struct mm_struct *);
> +
> +static inline int has_swap_token(struct mm_struct * mm)
> +{
> +	return (mm == swap_token_mm);
> +}
> +
> +static inline void put_swap_token(struct mm_struct * mm)
> +{
> +	if (has_swap_token(mm))
> +		__put_swap_token(mm);
> +}
> +#else /* CONFIG_SWAP */
> +#define put_swap_token do { } while(0)
> +#define grab_swap_token  do { } while(0)
> +#define has_swap_token 0
> +#endif /* CONFIG_SWAP */
>  
>  /* linux/mm/swapfile.c */
>  extern long total_swap_pages;
> --- linux-2.6.7/include/linux/sched.h.token	2004-07-30 13:22:28.000000000 -0400
> +++ linux-2.6.7/include/linux/sched.h	2004-07-30 13:22:29.000000000 -0400
> @@ -239,6 +239,10 @@
>  	/* Architecture-specific MM context */
>  	mm_context_t context;
>  
> +	/* Token based thrashing protection. */
> +	unsigned long swap_token_time;
> +	char recent_pagein;
> +
>  	/* coredumping support */
>  	int core_waiters;
>  	struct completion *core_startup_done, core_done;
> --- linux-2.6.7/kernel/fork.c.token	2004-07-30 13:22:27.000000000 -0400
> +++ linux-2.6.7/kernel/fork.c	2004-07-30 13:22:29.000000000 -0400
> @@ -36,6 +36,7 @@
>  #include <linux/mount.h>
>  #include <linux/audit.h>
>  #include <linux/rmap.h>
> +#include <linux/swap.h>
>  
>  #include <asm/pgtable.h>
>  #include <asm/pgalloc.h>
> @@ -463,6 +464,7 @@
>  		exit_aio(mm);
>  		exit_mmap(mm);
>  		mmdrop(mm);
> +		put_swap_token(mm);
>  	}
>  }
>  
> --- linux-2.6.7/mm/memory.c.token	2004-07-30 13:22:28.000000000 -0400
> +++ linux-2.6.7/mm/memory.c	2004-07-30 13:22:29.000000000 -0400
> @@ -1433,6 +1433,7 @@
>  		/* Had to read the page from swap area: Major fault */
>  		ret = VM_FAULT_MAJOR;
>  		inc_page_state(pgmajfault);
> +		grab_swap_token();
>  	}
>  
>  	mark_page_accessed(page);
> --- linux-2.6.7/mm/filemap.c.token	2004-07-30 13:22:28.000000000 -0400
> +++ linux-2.6.7/mm/filemap.c	2004-07-30 13:22:29.000000000 -0400
> @@ -1195,6 +1195,7 @@
>  	 * effect.
>  	 */
>  	error = page_cache_read(file, pgoff);
> +	grab_swap_token();
>  
>  	/*
>  	 * The page we want has now been added to the page cache.
> --- /dev/null	2003-09-15 09:40:47.000000000 -0400
> +++ linux-2.6.7/mm/thrash.c	2004-07-30 16:55:00.000000000 -0400
> @@ -0,0 +1,100 @@
> +/*
> + * mm/thrash.c
> + *
> + * Copyright (C) 2004, Red Hat, Inc.
> + * Copyright (C) 2004, Rik van Riel <riel@xxxxxxxxxx>
> + * Released under the GPL, see the file COPYING for details.
> + *
> + * Simple token based thrashing protection, using the algorithm
> + * described in:  http://www.cs.wm.edu/~sjiang/token.pdf
> + */
> +#include <linux/jiffies.h>
> +#include <linux/mm.h>
> +#include <linux/sched.h>
> +#include <linux/swap.h>
> +
> +static spinlock_t swap_token_lock = SPIN_LOCK_UNLOCKED;
> +static unsigned long swap_token_timeout;
> +unsigned long swap_token_check;
> +struct mm_struct * swap_token_mm = &init_mm;
> +
> +#define SWAP_TOKEN_CHECK_INTERVAL (HZ * 2)
> +#define SWAP_TOKEN_TIMEOUT (HZ * 300)
> +
> +/*
> + * Take the token away if the process had no page faults
> + * in the last interval, or if it has held the token for
> + * too long.
> + */
> +#define SWAP_TOKEN_ENOUGH_RSS 1
> +#define SWAP_TOKEN_TIMED_OUT 2
> +static int should_release_swap_token(struct mm_struct * mm)
> +{
> +	int ret = 0;
> +	if (!mm->recent_pagein)
> +		ret = SWAP_TOKEN_ENOUGH_RSS;
> +	else if (time_after(jiffies, swap_token_timeout))
> +		ret = SWAP_TOKEN_TIMED_OUT;
> +	mm->recent_pagein = 0;
> +	return ret;
> +}
> +
> +/*
> + * Try to grab the swapout protection token.  We only try to
> + * grab it once every TOKEN_CHECK_INTERVAL, both to prevent
> + * SMP lock contention and to check that the process that held
> + * the token before is no longer thrashing.
> + */
> +void grab_swap_token(void)
> +{
> +	struct mm_struct * mm;
> +	int reason;
> +
> +	/* We have the token. Let others know we still need it. */
> +	if (has_swap_token(current->mm)) {
> +		current->mm->recent_pagein = 1;
> +		return;
> +	}
> +
> +	if (time_after(jiffies, swap_token_check)) {
> +
> +		/* Can't get swapout protection if we exceed our RSS limit. */
> +		// if (current->mm->rss > current->mm->rlimit_rss)
> +		//	return;
> +
> +		/* ... or if we recently held the token. */
> +		if (time_before(jiffies, current->mm->swap_token_time))
> +			return;
> +
> +		if (!spin_trylock(&swap_token_lock))
> +			return;
> +
> +		swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
> +
> +		mm = swap_token_mm;
> +		if ((reason = should_release_swap_token(mm))) {
> +			unsigned long eligable = jiffies;
> +			if (reason == SWAP_TOKEN_TIMED_OUT) {
> +				eligable += SWAP_TOKEN_TIMEOUT;
> +			}
> +			mm->swap_token_time = eligable;
> +			swap_token_timeout = jiffies + SWAP_TOKEN_TIMEOUT;
> +			swap_token_mm = current->mm;
> +			printk("Took swap token, pid %d (%s)\n",
> +				 current->pid, current->comm);
> +		}
> +		spin_unlock(&swap_token_lock);
> +	}
> +	return;
> +}
> +
> +/* Called on process exit. */
> +void __put_swap_token(struct mm_struct * mm)
> +{
> +	spin_lock(&swap_token_lock);
> +	if (mm == swap_token_mm) {
> +		swap_token_mm = &init_mm;
> +		swap_token_check = jiffies;
> +	}
> +	spin_unlock(&swap_token_lock);
> +}
> --- linux-2.6.7/mm/rmap.c.token	2004-07-30 13:22:24.000000000 -0400
> +++ linux-2.6.7/mm/rmap.c	2004-07-30 13:22:29.000000000 -0400
> @@ -230,6 +230,9 @@
>  	if (ptep_clear_flush_young(vma, address, pte))
>  		referenced++;
>  
> +	if (mm != current->mm && has_swap_token(mm))
> +		referenced++;
> +
>  	(*mapcount)--;
>  
>  out_unmap:
> --- linux-2.6.7/mm/Makefile.token	2004-07-30 13:22:27.000000000 -0400
> +++ linux-2.6.7/mm/Makefile	2004-07-30 13:22:29.000000000 -0400
> @@ -12,7 +12,7 @@
>  			   readahead.o slab.o swap.o truncate.o vmscan.o \
>  			   $(mmu-y)
>  
> -obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o
> +obj-$(CONFIG_SWAP)	+= page_io.o swap_state.o swapfile.o thrash.o
>  obj-$(CONFIG_X86_4G)	+= usercopy.o
>  obj-$(CONFIG_HUGETLBFS)	+= hugetlb.o
>  obj-$(CONFIG_NUMA) 	+= mempolicy.o
> --
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