Re: [PATCH V3] MM: make vmpressure_win dynamic

[Fabian Frederick]

On Mon, 12 May 2014 09:55:37 +0200
Michal Hocko <mhocko@xxxxxxx> wrote:

> On Sat 10-05-14 08:52:17, Fabian Frederick wrote:
> > This patch addresses TODO featuring in original version :
> 
> This is the 3rd version of the patch and I still fail to see the
> motivation other than addressing a TODO which doesn't sound like a
> sufficient justification to me. Why is the new scheme needed in the
> first place? Why is calculate_normal_threshold a proper scheme?
Nothing more than trying to have that value dynamic.
As no one seems interested, let's just forget about that patch :)

Regards,
Fabian
> 
> > "Make the window size depend on machine size, as we do for vmstat"
> > 
> > It initializes vmpressure_win in vmstat using calculate_normal_threshold()
> > based on each zone/cpu * SWAP_CLUSTER_SIZE instead of
> > static SWAP_CLUSTER_MAX * 16 = 512
> > 
> > Some values :
> > 
> > CPU	MB	VMPRESSURE
> > 8	512	1024
> > 1	1024 	320
> > 2	1024 	640
> > 2	2048 	768
> > 4	2048	1152
> > 1	4096 	640
> > 4	4096 	1920
> > ...
> > 
> > (No maximum vmpressure value currently defined)
> > 
> > cf mm/vmstat.c: calculate_normal_threshold for further values
> > 
> > vmpressure_win is refreshed through cpu notifier and exposed read-only in
> > /proc/sys/vm/vmpressure_win
> > 
> > Cc: Tejun Heo <tj@xxxxxxxxxx>
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Michal Hocko <mhocko@xxxxxxx>
> > Cc: Davidlohr Bueso <davidlohr@xxxxxx>
> > Cc: Li Zefan <lizefan@xxxxxxxxxx>
> > Cc: cgroups@xxxxxxxxxxxxxxx
> > Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
> > ---
> > V3:
> >   -Further description
> >   -sysctl handler / ulong
> >   -Cc list
> > 
> > V2: Suggestions by Andrew Morton
> >   -Expose vmpressure_win
> >   -Remove spinlock
> > 
> >  include/linux/swap.h | 4 ++++
> >  kernel/sysctl.c      | 9 +++++++++
> >  mm/vmpressure.c      | 4 +---
> >  mm/vmstat.c          | 6 ++++++
> >  4 files changed, 20 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/linux/swap.h b/include/linux/swap.h
> > index 3507115..886897d 100644
> > --- a/include/linux/swap.h
> > +++ b/include/linux/swap.h
> > @@ -354,6 +354,10 @@ extern int vm_swappiness;
> >  extern int remove_mapping(struct address_space *mapping, struct page *page);
> >  extern unsigned long vm_total_pages;
> >  
> > +#ifdef CONFIG_MEMCG
> > +extern unsigned long vmpressure_win;
> > +#endif
> > +
> >  #ifdef CONFIG_NUMA
> >  extern int zone_reclaim_mode;
> >  extern int sysctl_min_unmapped_ratio;
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 74f5b58..c0c5ea6 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -1202,6 +1202,15 @@ static struct ctl_table vm_table[] = {
> >  		.mode           = 0444 /* read-only */,
> >  		.proc_handler   = pdflush_proc_obsolete,
> >  	},
> > +#ifdef CONFIG_MEMCG
> > +	{
> > +		.procname	= "vmpressure_window",
> > +		.data		= &vmpressure_win,
> > +		.maxlen		= sizeof(vmpressure_win),
> > +		.mode		= 0444,
> > +		.proc_handler	= proc_doulongvec_minmax,
> > +	},
> > +#endif
> >  	{
> >  		.procname	= "swappiness",
> >  		.data		= &vm_swappiness,
> > diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> > index d4042e7..d738670 100644
> > --- a/mm/vmpressure.c
> > +++ b/mm/vmpressure.c
> > @@ -35,10 +35,8 @@
> >   * As the vmscan reclaimer logic works with chunks which are multiple of
> >   * SWAP_CLUSTER_MAX, it makes sense to use it for the window size as well.
> >   *
> > - * TODO: Make the window size depend on machine size, as we do for vmstat
> > - * thresholds. Currently we set it to 512 pages (2MB for 4KB pages).
> >   */
> > -static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
> > +unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
> >  
> >  /*
> >   * These thresholds are used when we account memory pressure through
> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > index 302dd07..ede68fd 100644
> > --- a/mm/vmstat.c
> > +++ b/mm/vmstat.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/writeback.h>
> >  #include <linux/compaction.h>
> >  #include <linux/mm_inline.h>
> > +#include <linux/swap.h>
> >  
> >  #include "internal.h"
> >  
> > @@ -163,11 +164,13 @@ void refresh_zone_stat_thresholds(void)
> >  	struct zone *zone;
> >  	int cpu;
> >  	int threshold;
> > +	unsigned long new_vmpressure_win = 0;
> >  
> >  	for_each_populated_zone(zone) {
> >  		unsigned long max_drift, tolerate_drift;
> >  
> >  		threshold = calculate_normal_threshold(zone);
> > +		new_vmpressure_win += threshold;
> >  
> >  		for_each_online_cpu(cpu)
> >  			per_cpu_ptr(zone->pageset, cpu)->stat_threshold
> > @@ -184,6 +187,9 @@ void refresh_zone_stat_thresholds(void)
> >  			zone->percpu_drift_mark = high_wmark_pages(zone) +
> >  					max_drift;
> >  	}
> > +#ifdef CONFIG_MEMCG
> > +	vmpressure_win = new_vmpressure_win * SWAP_CLUSTER_MAX;
> > +#endif
> >  }
> >  
> >  void set_pgdat_percpu_threshold(pg_data_t *pgdat,
> > -- 
> > 1.8.4.5
> 
> -- 
> Michal Hocko
> SUSE Labs


-- 
Fabian Frederick <fabf@xxxxxxxxx>
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