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Message-Id: <1230682500.3470.3.camel@hermosa.site>
Date: Tue, 30 Dec 2008 17:15:00 -0700
From: "Peter W. Morreale" <pmorreale@...ell.com>
To: Randy Dunlap <randy.dunlap@...cle.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Add /proc controls for pdflush threads
On Tue, 2008-12-30 at 15:59 -0800, Randy Dunlap wrote:
> Peter W Morreale wrote:
> > From: \"Peter W. Morreale\" <pmorreale@...ell.com>
> >
> > This patch adds /proc entries to give the admin the ability to
> > control the minimum and maximum number of pdflush threads. This allows
> > finer control of pdflush on both large and small machines.
> >
> > The patch adds '/proc/sys/vm/nr_pdflush_threads_min' and
> > '/proc/sys/vm/nr_pdflush_threads_max' with r/w permissions.
>
> These need to be documented in (ugh) either
> Documentation/filesystems/proc.txt or
> Documentation/sysctl/vm.txt. Hard to say which one, but I'd
> recommend the latter (vm.txt) since they are sysctls.
>
Excellent point. Will re-spin.
Thx,
-PWM
>
> It looks like there is a lot of duplication between them.
> That's not good IMO.
>
> > ---
> >
> > Signed-off-by: Peter W Morreale <pmorreale@...ell.com>
> >
> > include/linux/sysctl.h | 2 ++
> > include/linux/writeback.h | 2 ++
> > kernel/sysctl.c | 16 ++++++++++++++++
> > mm/pdflush.c | 19 ++++++++++++++-----
> > 4 files changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> > index d0437f3..9921e62 100644
> > --- a/include/linux/sysctl.h
> > +++ b/include/linux/sysctl.h
> > @@ -205,6 +205,8 @@ enum
> > VM_PANIC_ON_OOM=33, /* panic at out-of-memory */
> > VM_VDSO_ENABLED=34, /* map VDSO into new processes? */
> > VM_MIN_SLAB=35, /* Percent pages ignored by zone reclaim */
> > + VM_NR_PDFLUSH_THREADS_MAX=36, /* nr_pdflush_threads_max */
> > + VM_NR_PDFLUSH_THREADS_MIN=37, /* nr_pdflush_threads_min */
> > };
> >
> >
> > diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> > index 12b15c5..ee566a0 100644
> > --- a/include/linux/writeback.h
> > +++ b/include/linux/writeback.h
> > @@ -150,6 +150,8 @@ void writeback_set_ratelimit(void);
> > /* pdflush.c */
> > extern int nr_pdflush_threads; /* Global so it can be exported to sysctl
> > read-only. */
> > +extern int nr_pdflush_threads_max; /* Global so it can be exported to sysctl */
> > +extern int nr_pdflush_threads_min; /* Global so it can be exported to sysctl */
> >
> >
> > #endif /* WRITEBACK_H */
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 50ec088..6dae777 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -948,6 +948,22 @@ static struct ctl_table vm_table[] = {
> > .proc_handler = &proc_dointvec,
> > },
> > {
> > + .ctl_name = VM_NR_PDFLUSH_THREADS_MIN,
> > + .procname = "nr_pdflush_threads_min",
> > + .data = &nr_pdflush_threads_min,
> > + .maxlen = sizeof nr_pdflush_threads_min,
> > + .mode = 0644 /* read-only*/,
> > + .proc_handler = &proc_dointvec,
> > + },
> > + {
> > + .ctl_name = VM_NR_PDFLUSH_THREADS_MAX,
> > + .procname = "nr_pdflush_threads_max",
> > + .data = &nr_pdflush_threads_max,
> > + .maxlen = sizeof nr_pdflush_threads_max,
> > + .mode = 0644 /* read-only*/,
> > + .proc_handler = &proc_dointvec,
> > + },
> > + {
> > .ctl_name = VM_SWAPPINESS,
> > .procname = "swappiness",
> > .data = &vm_swappiness,
> > diff --git a/mm/pdflush.c b/mm/pdflush.c
> > index 481680f..9a6f835 100644
> > --- a/mm/pdflush.c
> > +++ b/mm/pdflush.c
> > @@ -58,6 +58,14 @@ static DEFINE_SPINLOCK(pdflush_lock);
> > int nr_pdflush_threads = 0;
> >
> > /*
> > + * The max/min number of pdflush threads. R/W by sysctl at
> > + * /proc/sys/vm/nr_pdflush_threads_max
> > + */
> > +int nr_pdflush_threads_max = MAX_PDFLUSH_THREADS;
> > +int nr_pdflush_threads_min = MIN_PDFLUSH_THREADS;
> > +
> > +
> > +/*
> > * The time at which the pdflush thread pool last went empty
> > */
> > static unsigned long last_empty_jifs;
> > @@ -68,7 +76,7 @@ static unsigned long last_empty_jifs;
> > * Thread pool management algorithm:
> > *
> > * - The minimum and maximum number of pdflush instances are bound
> > - * by MIN_PDFLUSH_THREADS and MAX_PDFLUSH_THREADS.
> > + * by nr_pdflush_threads_min and nr_pdflush_threads_max.
> > *
> > * - If there have been no idle pdflush instances for 1 second, create
> > * a new one.
> > @@ -133,7 +141,8 @@ static int __pdflush(struct pdflush_work *my_work)
> > */
> > if (time_after(jiffies, last_empty_jifs + 1 * HZ)) {
> > if (list_empty(&pdflush_list)) {
> > - if (nr_pdflush_threads < MAX_PDFLUSH_THREADS) {
> > + if (nr_pdflush_threads <
> > + nr_pdflush_threads_max) {
> > nr_pdflush_threads++;
> > spin_unlock_irq(&pdflush_lock);
> > start_one_pdflush_thread();
> > @@ -150,7 +159,7 @@ static int __pdflush(struct pdflush_work *my_work)
> > */
> > if (list_empty(&pdflush_list))
> > continue;
> > - if (nr_pdflush_threads <= MIN_PDFLUSH_THREADS)
> > + if (nr_pdflush_threads <= nr_pdflush_threads_min)
> > continue;
> > pdf = list_entry(pdflush_list.prev, struct pdflush_work, list);
> > if (time_after(jiffies, pdf->when_i_went_to_sleep + 1 * HZ)) {
> > @@ -246,9 +255,9 @@ static int __init pdflush_init(void)
> > * Pre-set nr_pdflush_threads... If we fail to create,
> > * the count will be decremented.
> > */
> > - nr_pdflush_threads = MIN_PDFLUSH_THREADS;
> > + nr_pdflush_threads = nr_pdflush_threads_min;
> >
> > - for (i = 0; i < MIN_PDFLUSH_THREADS; i++)
> > + for (i = 0; i < nr_pdflush_threads_min; i++)
> > start_one_pdflush_thread();
> > return 0;
> > }
>
>
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