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Date: Mon, 12 May 2014 20:22:49 +0200
From: Fabian Frederick <fabf@...net.be>
To: Michal Hocko <mhocko@...e.cz>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Tejun Heo <tj@...nel.org>, akpm <akpm@...ux-foundation.org>,
Davidlohr Bueso <davidlohr@...com>,
Li Zefan <lizefan@...wei.com>,
cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH V3] MM: make vmpressure_win dynamic
On Mon, 12 May 2014 09:55:37 +0200
Michal Hocko <mhocko@...e.cz> 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@...nel.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Michal Hocko <mhocko@...e.cz>
> > Cc: Davidlohr Bueso <davidlohr@...com>
> > Cc: Li Zefan <lizefan@...wei.com>
> > Cc: cgroups@...r.kernel.org
> > Signed-off-by: Fabian Frederick <fabf@...net.be>
> > ---
> > 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@...net.be>
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