On Tuesday 28 February 2006 04:25, Andrew Morton wrote:
> "Rafael J. Wysocki" <[email protected]> wrote:
> >
> > Make shrink_all_memory() repeat the attempts to free more memory if there
> > seems to be no pages to free.
> >
>
> This description doesn't describe what the problem is, not how the patch
> fixes it. So I'm kinda left guessing.
I have described it in the 0/0 message, but I should have repeated that in the
changelog, sorry.
The probelm is that shrink_all_memory() sometimes returns 0 when there are
some freeable pages left. In swsusp we stop freeing memory when
shrink_all_memory() returns 0, so this is a problem to us.
> > ===================================================================
> > --- linux-2.6.16-rc4-mm2.orig/mm/vmscan.c
> > +++ linux-2.6.16-rc4-mm2/mm/vmscan.c
> > @@ -33,6 +33,7 @@
> > #include <linux/cpuset.h>
> > #include <linux/notifier.h>
> > #include <linux/rwsem.h>
> > +#include <linux/delay.h>
> >
> > #include <asm/tlbflush.h>
> > #include <asm/div64.h>
> > @@ -1793,17 +1794,24 @@ unsigned long shrink_all_memory(unsigned
> > struct reclaim_state reclaim_state = {
> > .reclaimed_slab = 0,
> > };
> > + int retry = 2;
> >
> > current->reclaim_state = &reclaim_state;
> > - for_each_pgdat(pgdat) {
> > - unsigned long freed;
> > + do {
> > + for_each_pgdat(pgdat) {
> > + unsigned long freed;
> >
> > - freed = balance_pgdat(pgdat, nr_to_free, 0);
> > - ret += freed;
> > - nr_to_free -= freed;
> > - if (nr_to_free <= 0)
> > + freed = balance_pgdat(pgdat, nr_to_free, 0);
> > + ret += freed;
> > + nr_to_free -= freed;
> > + if (nr_to_free <= 0)
> > + break;
> > + }
> > + if (ret > 0)
> > break;
> > - }
> > + if (retry)
> > + msleep_interruptible(100);
>
> TASK_INTERRUPTIBLE sleeps won't do anything if someone has sent this
> process a signal. They should be used with caution.
>
>
> Something like the below, I guess. But it's hard to fix something when you
> don't know what you're fixing.
Sorry again.
> swsusp should call drop_pagecache() and then drop_slab() before trying to
> use shrink_all_memory(), btw.
Well, sometimes we don't need to free a lot of memory.
> diff -puN mm/vmscan.c~mm-make-shrink_all_memory-try-harder mm/vmscan.c
> --- devel/mm/vmscan.c~mm-make-shrink_all_memory-try-harder 2006-02-27 19:17:29.000000000 -0800
> +++ devel-akpm/mm/vmscan.c 2006-02-27 19:21:08.000000000 -0800
> @@ -33,6 +33,7 @@
> #include <linux/cpuset.h>
> #include <linux/notifier.h>
> #include <linux/rwsem.h>
> +#include <linux/delay.h>
>
> #include <asm/tlbflush.h>
> #include <asm/div64.h>
> @@ -1783,11 +1784,13 @@ unsigned long shrink_all_memory(unsigned
> pg_data_t *pgdat;
> unsigned long nr_to_free = nr_pages;
> unsigned long ret = 0;
> + unsigned retry = 2;
> struct reclaim_state reclaim_state = {
> .reclaimed_slab = 0,
> };
>
> current->reclaim_state = &reclaim_state;
> +repeat:
> for_each_pgdat(pgdat) {
> unsigned long freed;
>
> @@ -1797,6 +1800,10 @@ unsigned long shrink_all_memory(unsigned
> if ((long)nr_to_free <= 0)
> break;
> }
> + if (retry-- && ret < nr_pages) {
> + blk_congestion_wait(WRITE, HZ/5);
> + goto repeat;
> + }
I'd like to do this only if ret is 0.
> current->reclaim_state = NULL;
> return ret;
> }
> _
>
> But then, the above could be implemented by the caller, so I don't know
> what's going on..
If 0 is returned, the caller assumes there are no more freeable pages.
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