lkml.org 
[lkml]   [2006]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [RFC][PATCH 2/2] Swap token re-tuned
From
Date
On Sat, 2006-09-30 at 00:35 +0530, Ashwin Chaugule wrote:
> New scheme to preempt token.
>
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@celunite.com>
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 34ed0d9..417bbe4 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -342,9 +342,15 @@ struct mm_struct {
> /* Architecture-specific MM context */
> mm_context_t context;
>
> - /* Token based thrashing protection. */
> - unsigned long swap_token_time;
> - char recent_pagein;
> + /* Swap token stuff */
> + /* Last value of global fault stamp as seen by this process.
> + * In other words, this value gives an indication of how long
> + * it has been since this task got the token */
> + unsigned int faultstamp;
> +
> + /* Deciding factor ! Increment if (global_faults - faultstamp < 5)
> + * else decrement. High priority wins the token.*/
> + int token_priority;

/*
* multi line comments look like this
*/

> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -910,6 +910,7 @@ #ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
> .extra1 = &zero,
> },
> #endif
> +#if 0 /* Not needed anymore */
> #ifdef CONFIG_SWAP
> {
> .ctl_name = VM_SWAP_TOKEN_TIMEOUT,
> @@ -921,6 +922,7 @@ #ifdef CONFIG_SWAP
> .strategy = &sysctl_jiffies,
> },
> #endif
> +#endif

Just remove it.

> 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;
> + if ( current->mm->token_priority > mm->token_priority )
> + return ret = SWAP_TOKEN_PREEMPT;
> + else
> + return ret;
> }

if (..)
ret = SWAP_TOKEN_PREEMPT;

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;
> + struct mm_struct *mm_temp;
> int reason;
> - /* We have the token. Let others know we still need it. */
> - if (has_swap_token(current->mm)) {
> - current->mm->recent_pagein = 1;
> - if (unlikely(!swap_token_default_timeout))
> - disable_swap_token();
> + /* This gives an indication of the number of processes contending for the token.*/

80 char max

> + global_faults++;
> +
> + if (!spin_trylock(&swap_token_lock))
> return;
> - }
>
> - if (time_after(jiffies, swap_token_check)) {
> + /* First come first served. If a process holding the token exits, its up for grabs immediately */

ditto

> + if ( swap_token_mm == NULL ) {
> + swap_token_mm = current->mm;
> + swap_token_mm->faultstamp = global_faults;
> + goto out;
> + }
>
> - if (!swap_token_default_timeout) {
> - swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
> - return;
> - }
> + if ((global_faults - current->mm->faultstamp) < FAULTSTAMP_DIFF ) {
>
> - /* ... or if we recently held the token. */
> - if (time_before(jiffies, current->mm->swap_token_time))
> - return;
> + /* This would mean that too many of the current tasks pages
> + * have been evicted and therefore it's calling swap-in or no-page
> + * too frequently. */

/*
* multi line coment
*/
> - if (!spin_trylock(&swap_token_lock))
> - return;
> + current->mm->faultstamp = global_faults;
> + current->mm->token_priority++;
> + mm_temp = swap_token_mm;
> + }
> + else {
> + /* Decrement priority to ensure that the token holder doesnt
> + * hold on to it for too long. */

more comments

> - swap_token_check = jiffies + SWAP_TOKEN_CHECK_INTERVAL;
> + if (current->mm->token_priority > 0)
> + current->mm->token_priority--;
> + else {
> + /* After this, the process will be able to contend for the token
> + * again.*/

ditto


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-09-29 21:27    [W:0.033 / U:0.096 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site