Re: why swap at all?

[FabF]

On Thu, 2004-06-03 at 01:54, Con Kolivas wrote:
> On Thu, 3 Jun 2004 04:30, FabF wrote:
> > On Wed, 2004-06-02 at 19:59, Valdis.Kletnieks@xxxxxx wrote:
> > > On Wed, 02 Jun 2004 07:38:41 +0200, FabF said:
> > > > > Yes but: your wm is so  often used/activated it will not get swaped 
> > > > > out. But if your mouse passes over mozilla and tries to focus it,
> > > > > then you will feel the pain of a swapped-out x program.
> > > >
> > > > Exactly !
> > > > Does autoregulated VM swap. patch could help here ?
> > >
> > > Con's auto-adjusting swappiness patch did in fact help that quite a bit,
> > > especially for the case of heavy file I/O causing process images to be
> > > swapped out.  I need to do some comparisons of that to Nick's MM work...
> >
> > It helps inactive applications to re-ermerge smoothly, heavy I/O and
> > global tuning.I've got 20 swapping delta from start to high usage.
> > That patch rock'n'roll my box until updatedb makes sw climbs up to 80
> > and freezes my box :(
> 
> Try this version instead which biases it downwards.
> 
> Con
> 
> ______________________________________________________________________
> diff -Naurp --exclude-from=dontdiff linux-2.6.7-rc2-base/include/linux/swap.h linux-2.6.7-rc2-am11/include/linux/swap.h
> --- linux-2.6.7-rc2-base/include/linux/swap.h	2004-05-31 21:29:21.000000000 +1000
> +++ linux-2.6.7-rc2-am11/include/linux/swap.h	2004-05-31 23:39:26.020055153 +1000
> @@ -175,6 +175,7 @@ extern void swap_setup(void);
>  extern int try_to_free_pages(struct zone **, unsigned int, unsigned int);
>  extern int shrink_all_memory(int);
>  extern int vm_swappiness;
> +extern int auto_swappiness;
>  
>  #ifdef CONFIG_MMU
>  /* linux/mm/shmem.c */
> diff -Naurp --exclude-from=dontdiff linux-2.6.7-rc2-base/include/linux/sysctl.h linux-2.6.7-rc2-am11/include/linux/sysctl.h
> --- linux-2.6.7-rc2-base/include/linux/sysctl.h	2004-05-31 21:29:21.000000000 +1000
> +++ linux-2.6.7-rc2-am11/include/linux/sysctl.h	2004-05-31 23:39:26.021054997 +1000
> @@ -164,6 +164,7 @@ enum
>  	VM_LAPTOP_MODE=23,	/* vm laptop mode */
>  	VM_BLOCK_DUMP=24,	/* block dump mode */
>  	VM_HUGETLB_GROUP=25,	/* permitted hugetlb group */
> +	VM_AUTO_SWAPPINESS=26,	/* Make vm_swappiness autoregulated */
>  };
>  
> 
> diff -Naurp --exclude-from=dontdiff linux-2.6.7-rc2-base/kernel/sysctl.c linux-2.6.7-rc2-am11/kernel/sysctl.c
> --- linux-2.6.7-rc2-base/kernel/sysctl.c	2004-05-31 21:29:24.000000000 +1000
> +++ linux-2.6.7-rc2-am11/kernel/sysctl.c	2004-05-31 23:40:57.658756170 +1000
> @@ -727,6 +727,14 @@ static ctl_table vm_table[] = {
>  		.extra1		= &zero,
>  		.extra2		= &one_hundred,
>  	},
> +	{
> +		.ctl_name	= VM_AUTO_SWAPPINESS,
> +		.procname	= "autoswappiness",
> +		.data		= &auto_swappiness,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= &proc_dointvec,
> +	},
>  #ifdef CONFIG_HUGETLB_PAGE
>  	 {
>  		.ctl_name	= VM_HUGETLB_PAGES,
> diff -Naurp --exclude-from=dontdiff linux-2.6.7-rc2-base/mm/vmscan.c linux-2.6.7-rc2-am11/mm/vmscan.c
> --- linux-2.6.7-rc2-base/mm/vmscan.c	2004-05-31 21:29:24.000000000 +1000
> +++ linux-2.6.7-rc2-am11/mm/vmscan.c	2004-05-31 23:39:26.051050316 +1000
> @@ -43,6 +43,7 @@
>   * From 0 .. 100.  Higher means more swappy.
>   */
>  int vm_swappiness = 60;
> +int auto_swappiness = 1;
>  static long total_memory;
>  
>  #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
> @@ -634,6 +635,41 @@ refill_inactive_zone(struct zone *zone, 
>  	 */
>  	mapped_ratio = (ps->nr_mapped * 100) / total_memory;
>  
> +	if (auto_swappiness) {
> +#ifdef CONFIG_SWAP
> +		int app_percent;
> +		struct sysinfo i;
> +		
> +		si_swapinfo(&i);
> +			
> +		if (likely(i.totalswap >= 100)) {
> +			int swap_centile;
> +	
> +			/*
> +			 * app_percent is the percentage of physical ram used
> +			 * by application pages.
> +			 */
> +			si_meminfo(&i);
> +			app_percent = 100 - ((i.freeram + get_page_cache_size() -
> +				swapper_space.nrpages) / (i.totalram / 100));
> +	
> +			/*
> +			 * swap_centile is the percentage of the last (sizeof physical
> +			 * ram) of swap free.
> +			 */
> +			swap_centile = i.freeswap / 
> +				(min(i.totalswap, i.totalram) / 100);
> +			/*
> +			 * Autoregulate vm_swappiness to be equal to the lowest of
> +			 * app_percent and swap_centile.  Bias it downwards -ck
> +			 */
> +			vm_swappiness = min(app_percent, swap_centile);
> +			vm_swappiness = vm_swappiness * vm_swappiness / 100;
> +		} else 
> +			vm_swappiness = 0;
> +#endif
> +	}
> +	
>  	/*
>  	 * Now decide how much we really want to unmap some pages.  The mapped
>  	 * ratio is downgraded - just because there's a lot of mapped memory
I've been unhappy with this one.sw range : 19->60.
So I've been playing slightly with sw curve replacing nerve centre with
:
vm_swappiness = vm_swappiness * vm_swappiness / 50;
if (vm_swappiness > 100)
        vm_swappiness = 100;

Results :
Warmup :Smooth, 30
Under pressure, swap grows roughly 60*60/50->72, 70*70/50->98 .... and
... rock'n'roll .... Box seems to keep the road this time.
updatedb gives side effects after 30 sec. though....sw drops to 70 ...
but I've got good global response.I guess we could expose curve
parameter.That one seems determinant :

vm_swappiness = vm_swappiness * vm_swappiness / swapcurve;
if (vm_swappiness > 100)
        vm_swappiness = 100;

and sysctl stuff as well :

	{
		.ctl_name	= VM_AUTO_SWAPPINESS,
		.procname	= "swapcurvature",
		.data		= &swapcurve,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_curvature,
	},

Regards,
FabF

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