On Mon, Oct 25, 2010 at 10:40:17AM +0800, KAMEZAWA Hiroyuki wrote:
> On Mon, 25 Oct 2010 10:47:31 +0800
> Bob Liu <lliubbo@xxxxxxxxx> wrote:
>
> > It's normal for isolate_lru_page() to fail at times. The failures are
> > typically temporal and may well go away when offline_pages() retries
> > the call. So it seems more reasonable to migrate as much as possible
> > to increase the chance of complete success in next retry.
> >
> > This patch remove page_count() check and remove putback_lru_pages() and
> > call migrate_pages() regardless of not_managed to reduce failure as much
> > as possible.
> >
> > Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx>
>
> -EBUSY should be returned.
It does return -EBUSY when ALL pages cannot be isolated from LRU (or
is non-LRU pages at all). That means offline_pages() will repeat calls
to do_migrate_range() as fast as possible as long as it can make
progress.
Is that behavior good enough? It does need some comment for this
non-obvious return value.
btw, the caller side code can be simplified (no behavior change).
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index dd186c1..606d358 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -848,17 +848,13 @@ repeat:
pfn = scan_lru_pages(start_pfn, end_pfn);
if (pfn) { /* We have page on LRU */
ret = do_migrate_range(pfn, end_pfn);
- if (!ret) {
- drain = 1;
- goto repeat;
- } else {
- if (ret < 0)
- if (--retry_max == 0)
- goto failed_removal;
+ if (ret < 0) {
+ if (--retry_max <= 0)
+ goto failed_removal;
yield();
- drain = 1;
- goto repeat;
}
+ drain = 1;
+ goto repeat;
}
/* drain all zone's lru pagevec, this is asyncronous... */
lru_add_drain_all();
Thanks,
Fengguang
> > ---
> > mm/memory_hotplug.c | 12 ------------
> > 1 files changed, 0 insertions(+), 12 deletions(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index a4cfcdc..b64cc9b 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -687,7 +687,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> > unsigned long pfn;
> > struct page *page;
> > int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
> > - int not_managed = 0;
> > int ret = 0;
> > LIST_HEAD(source);
> >
> > @@ -709,10 +708,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> > page_is_file_cache(page));
> >
> > } else {
> > - /* Becasue we don't have big zone->lock. we should
> > - check this again here. */
> > - if (page_count(page))
> > - not_managed++;
> > #ifdef CONFIG_DEBUG_VM
> > printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
> > pfn);
> > @@ -720,13 +715,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> > #endif
> > }
> > }
> > - ret = -EBUSY;
> > - if (not_managed) {
> > - if (!list_empty(&source))
> > - putback_lru_pages(&source);
> > - goto out;
> > - }
> > - ret = 0;
> > if (list_empty(&source))
> > goto out;
> > /* this function returns # of failed pages */
> > --
> > 1.6.3.3
> >
> >
--
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