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Subject[PATCH 05/10] mm/compaction: make "order" and "search_order" unsigned int in struct compact_control
Date
Objective
----
The "order"and "search_order" is int in struct compact_control. This
commit is aim to make "order" is unsigned int like other mm subsystem.

Change
----
1) Change "order" and "search_order" to unsigned int

2) Make is_via_compact_memory() return true when "order" is equal to
MAX_ORDER instead of -1, and rename it to is_manual_compaction() for
a clearer meaning.

3) Modify next_search_order() to fit unsigned order.

4) Restore fast_search_fail to unsigned int.
This is ok because search_order is already unsigned int, and after
reverting fast_search_fail to unsigned int, compact_control is still
within two cache lines.

Signed-off-by: Pengfei Li <lpf.vector@gmail.com>
---
mm/compaction.c | 96 +++++++++++++++++++++++++------------------------
mm/internal.h | 6 ++--
2 files changed, 53 insertions(+), 49 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 952dc2fb24e5..e47d8fa943a6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -75,7 +75,7 @@ static void split_map_pages(struct list_head *list)
list_for_each_entry_safe(page, next, list, lru) {
list_del(&page->lru);

- order = page_private(page);
+ order = page_order(page);
nr_pages = 1 << order;

post_alloc_hook(page, order, __GFP_MOVABLE);
@@ -879,7 +879,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* potential isolation targets.
*/
if (PageBuddy(page)) {
- unsigned long freepage_order = page_order_unsafe(page);
+ unsigned int freepage_order = page_order_unsafe(page);

/*
* Without lock, we cannot be sure that what we got is
@@ -1119,6 +1119,15 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
#ifdef CONFIG_COMPACTION

+/*
+ * order == MAX_ORDER is expected when compacting via
+ * /proc/sys/vm/compact_memory
+ */
+static inline bool is_manual_compaction(struct compact_control *cc)
+{
+ return cc->order == MAX_ORDER;
+}
+
static bool suitable_migration_source(struct compact_control *cc,
struct page *page)
{
@@ -1167,7 +1176,7 @@ static bool suitable_migration_target(struct compact_control *cc,
static inline unsigned int
freelist_scan_limit(struct compact_control *cc)
{
- unsigned short shift = BITS_PER_LONG - 1;
+ unsigned int shift = BITS_PER_LONG - 1;

return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
}
@@ -1253,21 +1262,24 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn, unsigned long
}

/* Search orders in round-robin fashion */
-static int next_search_order(struct compact_control *cc, int order)
+static unsigned int
+next_search_order(struct compact_control *cc, unsigned int order)
{
- order--;
- if (order < 0)
- order = cc->order - 1;
+ unsigned int next_order = order - 1;

- /* Search wrapped around? */
- if (order == cc->search_order) {
- cc->search_order--;
- if (cc->search_order < 0)
+ if (order == 0)
+ next_order = cc->order - 1;
+
+ if (next_order == cc->search_order) {
+ next_order = UINT_MAX;
+
+ order = cc->search_order;
+ cc->search_order -= 1;
+ if (order == 0)
cc->search_order = cc->order - 1;
- return -1;
}

- return order;
+ return next_order;
}

static unsigned long
@@ -1280,10 +1292,10 @@ fast_isolate_freepages(struct compact_control *cc)
unsigned long distance;
struct page *page = NULL;
bool scan_start = false;
- int order;
+ unsigned int order;

- /* Full compaction passes in a negative order */
- if (cc->order <= 0)
+ /* Full compaction when manual compaction */
+ if (is_manual_compaction(cc))
return cc->free_pfn;

/*
@@ -1310,10 +1322,10 @@ fast_isolate_freepages(struct compact_control *cc)
* Search starts from the last successful isolation order or the next
* order to search after a previous failure
*/
- cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
+ cc->search_order = min(cc->order - 1, cc->search_order);

for (order = cc->search_order;
- !page && order >= 0;
+ !page && order < MAX_ORDER;
order = next_search_order(cc, order)) {
struct free_area *area = &cc->zone->free_area[order];
struct list_head *freelist;
@@ -1837,15 +1849,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
}

-/*
- * order == -1 is expected when compacting via
- * /proc/sys/vm/compact_memory
- */
-static inline bool is_via_compact_memory(int order)
-{
- return order == -1;
-}
-
static enum compact_result __compact_finished(struct compact_control *cc)
{
unsigned int order;
@@ -1872,7 +1875,7 @@ static enum compact_result __compact_finished(struct compact_control *cc)
return COMPACT_PARTIAL_SKIPPED;
}

- if (is_via_compact_memory(cc->order))
+ if (is_manual_compaction(cc))
return COMPACT_CONTINUE;

/*
@@ -1962,9 +1965,6 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
{
unsigned long watermark;

- if (is_via_compact_memory(order))
- return COMPACT_CONTINUE;
-
watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
/*
* If watermarks for high-order allocation are already met, there
@@ -2071,7 +2071,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
static enum compact_result
compact_zone(struct compact_control *cc, struct capture_control *capc)
{
- enum compact_result ret;
+ enum compact_result ret = COMPACT_CONTINUE;
unsigned long start_pfn = cc->zone->zone_start_pfn;
unsigned long end_pfn = zone_end_pfn(cc->zone);
unsigned long last_migrated_pfn;
@@ -2079,21 +2079,25 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
bool update_cached;

cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
- ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
- cc->classzone_idx);
- /* Compaction is likely to fail */
- if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
- return ret;

- /* huh, compaction_suitable is returning something unexpected */
- VM_BUG_ON(ret != COMPACT_CONTINUE);
+ if (!is_manual_compaction(cc)) {
+ ret = compaction_suitable(cc->zone, cc->order,
+ cc->alloc_flags, cc->classzone_idx);

- /*
- * Clear pageblock skip if there were failures recently and compaction
- * is about to be retried after being deferred.
- */
- if (compaction_restarting(cc->zone, cc->order))
- __reset_isolation_suitable(cc->zone);
+ /* Compaction is likely to fail */
+ if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
+ return ret;
+
+ /* huh, compaction_suitable is returning something unexpected */
+ VM_BUG_ON(ret != COMPACT_CONTINUE);
+
+ /*
+ * Clear pageblock skip if there were failures recently and
+ * compaction is about to be retried after being deferred.
+ */
+ if (compaction_restarting(cc->zone, cc->order))
+ __reset_isolation_suitable(cc->zone);
+ }

/*
* Setup to move all movable pages to the end of the zone. Used cached
@@ -2407,7 +2411,7 @@ static void compact_node(int nid)
int zoneid;
struct zone *zone;
struct compact_control cc = {
- .order = -1,
+ .order = MAX_ORDER, /* is manual compaction */
.total_migrate_scanned = 0,
.total_free_scanned = 0,
.mode = MIGRATE_SYNC,
diff --git a/mm/internal.h b/mm/internal.h
index e32390802fd3..4e0ab641fb6c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -188,10 +188,10 @@ struct compact_control {
struct zone *zone;
unsigned long total_migrate_scanned;
unsigned long total_free_scanned;
- unsigned short fast_search_fail;/* failures to use free list searches */
- short search_order; /* order to start a fast search at */
+ unsigned int fast_search_fail; /* failures to use free list searches */
const gfp_t gfp_mask; /* gfp mask of a direct compactor */
- int order; /* order a direct compactor needs */
+ unsigned int order; /* order a direct compactor needs */
+ unsigned int search_order; /* order to start a fast search at */
int migratetype; /* migratetype of direct compactor */
const unsigned int alloc_flags; /* alloc flags of a direct compactor */
const int classzone_idx; /* zone index of a direct compactor */
--
2.21.0
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