From: yangge <yangge1116@xxxxxxx>
Since commit 984fdba6a32e ("mm, compaction: use proper alloc_flags
in __compaction_suitable()") allow compaction to proceed when free
pages required for compaction reside in the CMA pageblocks, it's
possible that __compaction_suitable() always returns true, and in
some cases, it's not acceptable.
There are 4 NUMA nodes on my machine, and each NUMA node has 32GB
of memory. I have configured 16GB of CMA memory on each NUMA node,
and starting a 32GB virtual machine with device passthrough is
extremely slow, taking almost an hour.
During the start-up of the virtual machine, it will call
pin_user_pages_remote(..., FOLL_LONGTERM, ...) to allocate memory.
Long term GUP cannot allocate memory from CMA area, so a maximum
of 16 GB of no-CMA memory on a NUMA node can be used as virtual
machine memory. Since there is 16G of free CMA memory on the NUMA
node, watermark for order-0 always be met for compaction, so
__compaction_suitable() always returns true, even if the node is
unable to allocate non-CMA memory for the virtual machine.
For costly allocations, because __compaction_suitable() always
returns true, __alloc_pages_slowpath() can't exit at the appropriate
place, resulting in excessively long virtual machine startup times.
Call trace:
__alloc_pages_slowpath
if (compact_result == COMPACT_SKIPPED ||
compact_result == COMPACT_DEFERRED)
goto nopage; // should exit __alloc_pages_slowpath() from here
In order to quickly fall back to remote node, we should remove
ALLOC_CMA both in __compaction_suitable() and __isolate_free_page()
in long term GUP flow. After this fix, starting a 32GB virtual machine
with device passthrough takes only a few seconds.
Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in __compaction_suitable()")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: yangge <yangge1116@xxxxxxx>
---
V5:
- add 'alloc_flags' parameter for __isolate_free_page()
- remove 'usa_cma' variable
V4:
- rich the commit log description
V3:
- fix build errors
- add ALLOC_CMA both in should_continue_reclaim() and compaction_ready()
V2:
- using the 'cc->alloc_flags' to determin if 'ALLOC_CMA' is needed
- rich the commit log description
include/linux/compaction.h | 6 ++++--
mm/compaction.c | 20 +++++++++++---------
mm/internal.h | 3 ++-
mm/page_alloc.c | 6 ++++--
mm/page_isolation.c | 3 ++-
mm/page_reporting.c | 2 +-
mm/vmscan.c | 4 ++--
7 files changed, 26 insertions(+), 18 deletions(-)
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index e947764..b4c3ac3 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -90,7 +90,8 @@ extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
struct page **page);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern bool compaction_suitable(struct zone *zone, int order,
- int highest_zoneidx);
+ int highest_zoneidx,
+ unsigned int alloc_flags);
extern void compaction_defer_reset(struct zone *zone, int order,
bool alloc_success);
@@ -108,7 +109,8 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat)
}
static inline bool compaction_suitable(struct zone *zone, int order,
- int highest_zoneidx)
+ int highest_zoneidx,
+ unsigned int alloc_flags)
{
return false;
}
diff --git a/mm/compaction.c b/mm/compaction.c
index 07bd227..b10d921 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -655,7 +655,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
/* Found a free page, will break it into order-0 pages */
order = buddy_order(page);
- isolated = __isolate_free_page(page, order);
+ isolated = __isolate_free_page(page, order, cc->alloc_flags);
if (!isolated)
break;
set_page_private(page, order);
@@ -1634,7 +1634,7 @@ static void fast_isolate_freepages(struct compact_control *cc)
/* Isolate the page if available */
if (page) {
- if (__isolate_free_page(page, order)) {
+ if (__isolate_free_page(page, order, cc->alloc_flags)) {
set_page_private(page, order);
nr_isolated = 1 << order;
nr_scanned += nr_isolated - 1;
@@ -2381,6 +2381,7 @@ static enum compact_result compact_finished(struct compact_control *cc)
static bool __compaction_suitable(struct zone *zone, int order,
int highest_zoneidx,
+ unsigned int alloc_flags,
unsigned long wmark_target)
{
unsigned long watermark;
@@ -2395,25 +2396,26 @@ static bool __compaction_suitable(struct zone *zone, int order,
* even if compaction succeeds.
* For costly orders, we require low watermark instead of min for
* compaction to proceed to increase its chances.
- * ALLOC_CMA is used, as pages in CMA pageblocks are considered
- * suitable migration targets
+ * In addition to long term GUP flow, ALLOC_CMA is used, as pages in
+ * CMA pageblocks are considered suitable migration targets
*/
watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
low_wmark_pages(zone) : min_wmark_pages(zone);
watermark += compact_gap(order);
return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
- ALLOC_CMA, wmark_target);
+ alloc_flags & ALLOC_CMA, wmark_target);
}
/*
* compaction_suitable: Is this suitable to run compaction on this zone now?
*/
-bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx)
+bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx,
+ unsigned int alloc_flags)
{
enum compact_result compact_result;
bool suitable;
- suitable = __compaction_suitable(zone, order, highest_zoneidx,
+ suitable = __compaction_suitable(zone, order, highest_zoneidx, alloc_flags,
zone_page_state(zone, NR_FREE_PAGES));
/*
* fragmentation index determines if allocation failures are due to
@@ -2474,7 +2476,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
available = zone_reclaimable_pages(zone) / order;
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
if (__compaction_suitable(zone, order, ac->highest_zoneidx,
- available))
+ alloc_flags, available))
return true;
}
@@ -2499,7 +2501,7 @@ compaction_suit_allocation_order(struct zone *zone, unsigned int order,
alloc_flags))
return COMPACT_SUCCESS;
- if (!compaction_suitable(zone, order, highest_zoneidx))
+ if (!compaction_suitable(zone, order, highest_zoneidx, alloc_flags))
return COMPACT_SKIPPED;
return COMPACT_CONTINUE;
diff --git a/mm/internal.h b/mm/internal.h
index 3922788..6d257c8 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -662,7 +662,8 @@ static inline void clear_zone_contiguous(struct zone *zone)
zone->contiguous = false;
}
-extern int __isolate_free_page(struct page *page, unsigned int order);
+extern int __isolate_free_page(struct page *page, unsigned int order,
+ unsigned int alloc_flags);
extern void __putback_isolated_page(struct page *page, unsigned int order,
int mt);
extern void memblock_free_pages(struct page *page, unsigned long pfn,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index dde19db..ecb2fd7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2809,7 +2809,8 @@ void split_page(struct page *page, unsigned int order)
}
EXPORT_SYMBOL_GPL(split_page);
-int __isolate_free_page(struct page *page, unsigned int order)
+int __isolate_free_page(struct page *page, unsigned int order,
+ unsigned int alloc_flags)
{
struct zone *zone = page_zone(page);
int mt = get_pageblock_migratetype(page);
@@ -2823,7 +2824,8 @@ int __isolate_free_page(struct page *page, unsigned int order)
* exists.
*/
watermark = zone->_watermark[WMARK_MIN] + (1UL << order);
- if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
+ if (!zone_watermark_ok(zone, 0, watermark, 0,
+ alloc_flags & ALLOC_CMA))
return 0;
}
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c608e9d..a1f2c79 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -229,7 +229,8 @@ static void unset_migratetype_isolate(struct page *page, int migratetype)
buddy = find_buddy_page_pfn(page, page_to_pfn(page),
order, NULL);
if (buddy && !is_migrate_isolate_page(buddy)) {
- isolated_page = !!__isolate_free_page(page, order);
+ isolated_page = !!__isolate_free_page(page, order,
+ ALLOC_CMA);
/*
* Isolating a free page in an isolated pageblock
* is expected to always work as watermarks don't
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index e4c428e..fd3813b 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -198,7 +198,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
/* Attempt to pull page from list and place in scatterlist */
if (*offset) {
- if (!__isolate_free_page(page, order)) {
+ if (!__isolate_free_page(page, order, ALLOC_CMA)) {
next = page;
break;
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5e03a61..33f5b46 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5815,7 +5815,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
sc->reclaim_idx, 0))
return false;
- if (compaction_suitable(zone, sc->order, sc->reclaim_idx))
+ if (compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA))
return false;
}
@@ -6043,7 +6043,7 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
return true;
/* Compaction cannot yet proceed. Do reclaim. */
- if (!compaction_suitable(zone, sc->order, sc->reclaim_idx))
+ if (!compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA))
return false;
/*
--
2.7.4
