Re: ppoll() stuck on POLLIN while TCP peer is sending

Mel Gorman
2013-01-09T13:50:21Z

On Wed, Jan 09, 2013 at 01:37:46PM +0000, Mel Gorman wrote:
> On Tue, Jan 08, 2013 at 11:23:25PM +0000, Eric Wong wrote:
> > Mel Gorman <mgorman@suse.de> wrote:
> > > Please try the following patch. However, even if it works the benefit of
> > > capture may be so marginal that partially reverting it and simplifying
> > > compaction.c is the better decision.
> >
> > I already got my VM stuck on this one. I had two twosleepy instances,
> > 2774 was the one that got stuck (also confirmed by watching top).
> >
>
> page->pfmemalloc can be left set for captured pages so try this but as
> capture is rarely used I'm strongly favouring a partial revert even if
> this works for you.

Partial revert looks like this

---8<---

---
include/linux/compaction.h | 4 +-
include/linux/mm.h | 1 -
mm/compaction.c | 91 ++++++--------------------------------------
mm/internal.h | 1 -
mm/page_alloc.c | 38 +++++-------------
5 files changed, 23 insertions(+), 112 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 6ecb6dc..cc7bdde 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -22,7 +22,7 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *mask,
- bool sync, bool *contended, struct page **page);
+ bool sync, bool *contended);
extern int compact_pgdat(pg_data_t *pgdat, int order);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern unsigned long compaction_suitable(struct zone *zone, int order);
@@ -75,7 +75,7 @@ static inline bool compaction_restarting(struct zone *zone, int order)
#else
static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- bool sync, bool *contended, struct page **page)
+ bool sync, bool *contended)
{
return COMPACT_CONTINUE;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6320407..66e2f7c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -455,7 +455,6 @@ void put_pages_list(struct list_head *pages);

void split_page(struct page *page, unsigned int order);
int split_free_page(struct page *page);
-int capture_free_page(struct page *page, int alloc_order, int migratetype);

/*
* Compound pages have a destructor function. Provide a
diff --git a/mm/compaction.c b/mm/compaction.c
index 6b807e4..8bc3066 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -816,6 +816,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
static int compact_finished(struct zone *zone,
struct compact_control *cc)
{
+ unsigned int order;
unsigned long watermark;

if (fatal_signal_pending(current))
@@ -850,22 +851,15 @@ static int compact_finished(struct zone *zone,
return COMPACT_CONTINUE;

/* Direct compactor: Is a suitable page free? */
- if (cc->page) {
- /* Was a suitable page captured? */
- if (*cc->page)
+ for (order = cc->order; order < MAX_ORDER; order++) {
+ struct free_area *area = &zone->free_area[cc->order];
+ /* Job done if page is free of the right migratetype */
+ if (!list_empty(&area->free_list[cc->migratetype]))
+ return COMPACT_PARTIAL;
+
+ /* Job done if allocation would set block type */
+ if (cc->order >= pageblock_order && area->nr_free)
return COMPACT_PARTIAL;
- } else {
- unsigned int order;
- for (order = cc->order; order < MAX_ORDER; order++) {
- struct free_area *area = &zone->free_area[cc->order];
- /* Job done if page is free of the right migratetype */
- if (!list_empty(&area->free_list[cc->migratetype]))
- return COMPACT_PARTIAL;
-
- /* Job done if allocation would set block type */
- if (cc->order >= pageblock_order && area->nr_free)
- return COMPACT_PARTIAL;
- }
}

return COMPACT_CONTINUE;
@@ -921,60 +915,6 @@ unsigned long compaction_suitable(struct zone *zone, int order)
return COMPACT_CONTINUE;
}

-static void compact_capture_page(struct compact_control *cc)
-{
- unsigned long flags;
- int mtype, mtype_low, mtype_high;
-
- if (!cc->page || *cc->page)
- return;
-
- /*
- * For MIGRATE_MOVABLE allocations we capture a suitable page ASAP
- * regardless of the migratetype of the freelist is is captured from.
- * This is fine because the order for a high-order MIGRATE_MOVABLE
- * allocation is typically at least a pageblock size and overall
- * fragmentation is not impaired. Other allocation types must
- * capture pages from their own migratelist because otherwise they
- * could pollute other pageblocks like MIGRATE_MOVABLE with
- * difficult to move pages and making fragmentation worse overall.
- */
- if (cc->migratetype == MIGRATE_MOVABLE) {
- mtype_low = 0;
- mtype_high = MIGRATE_PCPTYPES;
- } else {
- mtype_low = cc->migratetype;
- mtype_high = cc->migratetype + 1;
- }
-
- /* Speculatively examine the free lists without zone lock */
- for (mtype = mtype_low; mtype < mtype_high; mtype++) {
- int order;
- for (order = cc->order; order < MAX_ORDER; order++) {
- struct page *page;
- struct free_area *area;
- area = &(cc->zone->free_area[order]);
- if (list_empty(&area->free_list[mtype]))
- continue;
-
- /* Take the lock and attempt capture of the page */
- if (!compact_trylock_irqsave(&cc->zone->lock, &flags, cc))
- return;
- if (!list_empty(&area->free_list[mtype])) {
- page = list_entry(area->free_list[mtype].next,
- struct page, lru);
- if (capture_free_page(page, cc->order, mtype)) {
- spin_unlock_irqrestore(&cc->zone->lock,
- flags);
- *cc->page = page;
- return;
- }
- }
- spin_unlock_irqrestore(&cc->zone->lock, flags);
- }
- }
-}
-
static int compact_zone(struct zone *zone, struct compact_control *cc)
{
int ret;
@@ -1054,9 +994,6 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
goto out;
}
}
-
- /* Capture a page now if it is a suitable size */
- compact_capture_page(cc);
}

out:
@@ -1069,8 +1006,7 @@ out:

static unsigned long compact_zone_order(struct zone *zone,
int order, gfp_t gfp_mask,
- bool sync, bool *contended,
- struct page **page)
+ bool sync, bool *contended)
{
unsigned long ret;
struct compact_control cc = {
@@ -1080,7 +1016,6 @@ static unsigned long compact_zone_order(struct zone *zone,
.migratetype = allocflags_to_migratetype(gfp_mask),
.zone = zone,
.sync = sync,
- .page = page,
};
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
@@ -1110,7 +1045,7 @@ int sysctl_extfrag_threshold = 500;
*/
unsigned long try_to_compact_pages(struct zonelist *zonelist,
int order, gfp_t gfp_mask, nodemask_t *nodemask,
- bool sync, bool *contended, struct page **page)
+ bool sync, bool *contended)
{
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
int may_enter_fs = gfp_mask & __GFP_FS;
@@ -1136,7 +1071,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
int status;

status = compact_zone_order(zone, order, gfp_mask, sync,
- contended, page);
+ contended);
rc = max(status, rc);

/* If a normal allocation would succeed, stop compacting */
@@ -1192,7 +1127,6 @@ int compact_pgdat(pg_data_t *pgdat, int order)
struct compact_control cc = {
.order = order,
.sync = false,
- .page = NULL,
};

return __compact_pgdat(pgdat, &cc);
@@ -1203,7 +1137,6 @@ static int compact_node(int nid)
struct compact_control cc = {
.order = -1,
.sync = true,
- .page = NULL,
};

return __compact_pgdat(NODE_DATA(nid), &cc);
diff --git a/mm/internal.h b/mm/internal.h
index d597f94..9ba2110 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -135,7 +135,6 @@ struct compact_control {
int migratetype; /* MOVABLE, RECLAIMABLE etc */
struct zone *zone;
bool contended; /* True if a lock was contended */
- struct page **page; /* Page captured of requested size */
};

unsigned long
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4ba5e37..ebf7fd8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1389,22 +1389,14 @@ void split_page(struct page *page, unsigned int order)
set_page_refcounted(page + i);
}

-/*
- * Similar to the split_page family of functions except that the page
- * required at the given order and being isolated now to prevent races
- * with parallel allocators
- */
-int capture_free_page(struct page *page, int alloc_order, int migratetype)
+static int __isolate_free_page(struct page *page, unsigned int order)
{
- unsigned int order;
unsigned long watermark;
struct zone *zone;
int mt;

BUG_ON(!PageBuddy(page));
-
zone = page_zone(page);
- order = page_order(page);
mt = get_pageblock_migratetype(page);

if (mt != MIGRATE_ISOLATE) {
@@ -1413,7 +1405,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
return 0;

- __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt);
+ __mod_zone_freepage_state(zone, -(1UL << order), mt);
}

/* Remove page from free list */
@@ -1421,11 +1413,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
zone->free_area[order].nr_free--;
rmv_page_order(page);

- if (alloc_order != order)
- expand(zone, page, alloc_order, order,
- &zone->free_area[order], migratetype);
-
- /* Set the pageblock if the captured page is at least a pageblock */
+ /* Set the pageblock if the isolated page is at least a pageblock */
if (order >= pageblock_order - 1) {
struct page *endpage = page + (1 << order) - 1;
for (; page < endpage; page += pageblock_nr_pages) {
@@ -1436,7 +1424,7 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
}
}

- return 1UL << alloc_order;
+ return 1UL << order;
}

/*
@@ -1451,13 +1439,12 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
*/
int split_free_page(struct page *page)
{
- unsigned int order;
+ unsigned int order = page_order(page);
int nr_pages;

- BUG_ON(!PageBuddy(page));
order = page_order(page);

- nr_pages = capture_free_page(page, order, 0);
+ nr_pages = __isolate_free_page(page, order);
if (!nr_pages)
return 0;

@@ -2163,8 +2150,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
bool *contended_compaction, bool *deferred_compaction,
unsigned long *did_some_progress)
{
- struct page *page = NULL;
-
if (!order)
return NULL;

@@ -2176,16 +2161,12 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
current->flags |= PF_MEMALLOC;
*did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
nodemask, sync_migration,
- contended_compaction, &page);
+ contended_compaction);
current->flags &= ~PF_MEMALLOC;

- /* If compaction captured a page, prep and use it */
- if (page) {
- prep_new_page(page, order, gfp_mask);
- goto got_page;
- }
-
if (*did_some_progress != COMPACT_SKIPPED) {
+ struct page *page;
+
/* Page migration frees to the PCP lists but we want merging */
drain_pages(get_cpu());
put_cpu();
@@ -2195,7 +2176,6 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
alloc_flags & ~ALLOC_NO_WATERMARKS,
preferred_zone, migratetype);
if (page) {
-got_page:
preferred_zone->compact_blockskip_flush = false;
preferred_zone->compact_considered = 0;
preferred_zone->compact_defer_shift = 0;