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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_COMPACTION_H
#define _LINUX_COMPACTION_H
/*
* Determines how hard direct compaction should try to succeed.
* Lower value means higher priority, analogically to reclaim priority.
*/
enum compact_priority {
COMPACT_PRIO_SYNC_FULL,
MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
COMPACT_PRIO_SYNC_LIGHT,
MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
COMPACT_PRIO_ASYNC,
INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
};
/* Return values for compact_zone() and try_to_compact_pages() */
/* When adding new states, please adjust include/trace/events/compaction.h */
enum compact_result {
/* For more detailed tracepoint output - internal to compaction */
COMPACT_NOT_SUITABLE_ZONE,
/*
* compaction didn't start as it was not possible or direct reclaim
* was more suitable
*/
COMPACT_SKIPPED,
/* compaction didn't start as it was deferred due to past failures */
COMPACT_DEFERRED,
/* For more detailed tracepoint output - internal to compaction */
COMPACT_NO_SUITABLE_PAGE,
/* compaction should continue to another pageblock */
COMPACT_CONTINUE,
/*
* The full zone was compacted scanned but wasn't successfull to compact
* suitable pages.
*/
COMPACT_COMPLETE,
/*
* direct compaction has scanned part of the zone but wasn't successfull
* to compact suitable pages.
*/
COMPACT_PARTIAL_SKIPPED,
/* compaction terminated prematurely due to lock contentions */
COMPACT_CONTENDED,
/*
* direct compaction terminated after concluding that the allocation
* should now succeed
*/
COMPACT_SUCCESS,
};
struct alloc_context; /* in mm/internal.h */
/*
* Number of free order-0 pages that should be available above given watermark
* to make sure compaction has reasonable chance of not running out of free
* pages that it needs to isolate as migration target during its work.
*/
static inline unsigned long compact_gap(unsigned int order)
{
/*
* Although all the isolations for migration are temporary, compaction
* free scanner may have up to 1 << order pages on its list and then
* try to split an (order - 1) free page. At that point, a gap of
* 1 << order might not be enough, so it's safer to require twice that
* amount. Note that the number of pages on the list is also
* effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
* that the migrate scanner can have isolated on migrate list, and free
* scanner is only invoked when the number of isolated free pages is
* lower than that. But it's not worth to complicate the formula here
* as a bigger gap for higher orders than strictly necessary can also
* improve chances of compaction success.
*/
return 2UL << order;
}
#ifdef CONFIG_COMPACTION
extern unsigned int sysctl_compaction_proactiveness;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
void *buffer, size_t *length, loff_t *ppos);
extern int sysctl_extfrag_threshold;
extern int sysctl_compact_unevictable_allowed;
extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
unsigned int order, unsigned int alloc_flags,
const struct alloc_context *ac, enum compact_priority prio,
struct page **page);
extern void reset_isolation_suitable(pg_data_t *pgdat);
extern enum compact_result compaction_suitable(struct zone *zone, int order,
unsigned int alloc_flags, int highest_zoneidx);
extern void compaction_defer_reset(struct zone *zone, int order,
bool alloc_success);
/* Compaction has made some progress and retrying makes sense */
static inline bool compaction_made_progress(enum compact_result result)
{
/*
* Even though this might sound confusing this in fact tells us
* that the compaction successfully isolated and migrated some
* pageblocks.
*/
if (result == COMPACT_SUCCESS)
return true;
return false;
}
/* Compaction has failed and it doesn't make much sense to keep retrying. */
static inline bool compaction_failed(enum compact_result result)
{
/* All zones were scanned completely and still not result. */
if (result == COMPACT_COMPLETE)
return true;
return false;
}
/* Compaction needs reclaim to be performed first, so it can continue. */
static inline bool compaction_needs_reclaim(enum compact_result result)
{
/*
* Compaction backed off due to watermark checks for order-0
* so the regular reclaim has to try harder and reclaim something.
*/
if (result == COMPACT_SKIPPED)
return true;
return false;
}
/*
* Compaction has backed off for some reason after doing some work or none
* at all. It might be throttling or lock contention. Retrying might be still
* worthwhile, but with a higher priority if allowed.
*/
static inline bool compaction_withdrawn(enum compact_result result)
{
/*
* If compaction is deferred for high-order allocations, it is
* because sync compaction recently failed. If this is the case
* and the caller requested a THP allocation, we do not want
* to heavily disrupt the system, so we fail the allocation
* instead of entering direct reclaim.
*/
if (result == COMPACT_DEFERRED)
return true;
/*
* If compaction in async mode encounters contention or blocks higher
* priority task we back off early rather than cause stalls.
*/
if (result == COMPACT_CONTENDED)
return true;
/*
* Page scanners have met but we haven't scanned full zones so this
* is a back off in fact.
*/
if (result == COMPACT_PARTIAL_SKIPPED)
return true;
return false;
}
bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
int alloc_flags);
extern int kcompactd_run(int nid);
extern void kcompactd_stop(int nid);
extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
#else
static inline void reset_isolation_suitable(pg_data_t *pgdat)
{
}
static inline enum compact_result compaction_suitable(struct zone *zone, int order,
int alloc_flags, int highest_zoneidx)
{
return COMPACT_SKIPPED;
}
static inline bool compaction_made_progress(enum compact_result result)
{
return false;
}
static inline bool compaction_failed(enum compact_result result)
{
return false;
}
static inline bool compaction_needs_reclaim(enum compact_result result)
{
return false;
}
static inline bool compaction_withdrawn(enum compact_result result)
{
return true;
}
static inline int kcompactd_run(int nid)
{
return 0;
}
static inline void kcompactd_stop(int nid)
{
}
static inline void wakeup_kcompactd(pg_data_t *pgdat,
int order, int highest_zoneidx)
{
}
#endif /* CONFIG_COMPACTION */
struct node;
#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
extern int compaction_register_node(struct node *node);
extern void compaction_unregister_node(struct node *node);
#else
static inline int compaction_register_node(struct node *node)
{
return 0;
}
static inline void compaction_unregister_node(struct node *node)
{
}
#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
#endif /* _LINUX_COMPACTION_H */
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