mm: zone lock tracepoint instrumentation
Subsystems (8)
v2 cover mm: zone lock tracepoint instrumentation
Zone lock contention can significantly impact allocation and reclaim latency, as it is a central synchronization point in the page allocator and reclaim paths. Improved visibility into its behavior is therefore important for diagnosing performance issues in memory-intensive workloads.
On some production workloads at Meta, we have observed noticeable zone lock contention. Deeper analysis of lock holders and waiters is currently difficult with existing instrumentation.
While generic lock contention_begin/contention_end tracepoints cover the slow path, they do not provide sufficient visibility into lock hold times. In particular, the lack of a release-side event makes it difficult to identify long lock holders and correlate them with waiters. As a result, distinguishing between short bursts of contention and pathological long hold times requires additional instrumentation.
This patch series adds dedicated tracepoint instrumentation to zone lock, following the existing mmap_lock tracing model.
The goal is to enable detailed holder/waiter analysis and lock hold time measurements without affecting the fast path when tracing is disabled.
The series is structured as follows:
1. Introduce zone lock wrappers.
2. Mechanically convert zone lock users to the wrappers.
3. Convert compaction to use the wrappers (requires minor restructuring of compact_lock_irqsave()).
4. Add zone lock tracepoints.
The tracepoints are added via lightweight inline helpers in the wrappers. When tracing is disabled, the fast path remains unchanged.
The compaction changes required abstracting compact_lock_irqsave() away from raw spinlock_t. I chose a small tagged struct to handle both zone and LRU locks uniformly. If there is a preferred alternative (e.g. splitting helpers or using a different abstraction), I would appreciate feedback.
Changes in v2:
- Move mecanical changes from mm/compaction.c to different commit.
- Removed compact_do_zone_trylock() and compact_do_raw_trylock_irqsave().
Dmitry Ilvokhin (4):
mm: introduce zone lock wrappers
mm: convert zone lock users to wrappers
mm: convert compaction to zone lock wrappers
mm: add tracepoints for zone lock
MAINTAINERS | 3 + include/linux/zone_lock.h | 100 +++++++++++++++++++++++++++++++ include/trace/events/zone_lock.h | 64 ++++++++++++++++++++ mm/Makefile | 2 +- mm/compaction.c | 96 +++++++++++++++++++++++------ mm/memory_hotplug.c | 9 +-- mm/mm_init.c | 3 +- mm/page_alloc.c | 73 +++++++++++----------- mm/page_isolation.c | 19 +++--- mm/page_reporting.c | 13 ++-- mm/show_mem.c | 5 +- mm/vmscan.c | 5 +- mm/vmstat.c | 9 +-- mm/zone_lock.c | 31 ++++++++++ 14 files changed, 348 insertions(+), 84 deletions(-) create mode 100644 include/linux/zone_lock.h create mode 100644 include/trace/events/zone_lock.h create mode 100644 mm/zone_lock.c
Signature · 1 line
2.47.3
PATCH v2 1/4 mm: introduce zone lock wrappers
Add thin wrappers around zone lock acquire/release operations. This prepares the code for future tracepoint instrumentation without modifying individual call sites.
Centralizing zone lock operations behind wrappers allows future instrumentation or debugging hooks to be added without touching all users.
No functional change intended. The wrappers are introduced in preparation for subsequent patches and are not yet used.
--- MAINTAINERS | 1 + include/linux/zone_lock.h | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+) create mode 100644 include/linux/zone_lock.h
MAINTAINERS +1 -0
@@ -16680,6 +16680,7 @@ F: include/linux/pgtable.h F: include/linux/ptdump.h F: include/linux/vmpressure.h F: include/linux/vmstat.h +F: include/linux/zone_lock.h F: kernel/fork.c F: mm/Kconfig F: mm/debug.c
include/linux/zone_lock.h new file +38 -0
@@ -0,0 +1,38 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_ZONE_LOCK_H +#define _LINUX_ZONE_LOCK_H + +#include <linux/mmzone.h> +#include <linux/spinlock.h> + +static inline void zone_lock_init (struct zone *zone) +{ +spin_lock_init (&zone->lock); +} + +#define zone_lock_irqsave (zone, flags) \ +do { \ + spin_lock_irqsave(&(zone)->lock, flags); \ +} while (0) + +#define zone_trylock_irqsave (zone, flags) \ +({ \ + spin_trylock_irqsave(&(zone)->lock, flags); \ +}) + +static inline void zone_unlock_irqrestore (struct zone *zone,unsigned long flags) +{ +spin_unlock_irqrestore (&zone->lock, flags); +} + +static inline void zone_lock_irq (struct zone *zone) +{ +spin_lock_irq (&zone->lock); +} + +static inline void zone_unlock_irq (struct zone *zone) +{ +spin_unlock_irq (&zone->lock); +} + +#endif /* _LINUX_ZONE_LOCK_H */
Signature · 1 line
2.47.3
Andrew Morton
maintainerRe: [PATCH v2 1/4] mm: introduce zone lock wrappers
Quoted 13 lines · On Wed, 25 Feb 2026 14:43:03 +0000 Dmitry Ilvokhin <[email protected]> wrote:
Add thin wrappers around zone lock acquire/release operations. This prepares the code for future tracepoint instrumentation without modifying individual call sites.
Centralizing zone lock operations behind wrappers allows future instrumentation or debugging hooks to be added without touching all users.
No functional change intended. The wrappers are introduced in preparation for subsequent patches and are not yet used.
...
include/linux/zone_lock.h line 11
Quoted 4 lines
include/linux/zone_lock.h new file +4
-0+static inline void zone_lock_init (struct zone *zone) +{ +spin_lock_init (&zone->lock); +}
Please consider renaming zone.lock to something else (_lock would be conventional) so that any present and future and out-of-tree unconverted code won't compile.
Re: [PATCH v2 1/4] mm: introduce zone lock wrappers
Quoted 15 lines · Andrew Morton
Quoted 13 lines · On Wed, 25 Feb 2026 14:43:03 +0000 Dmitry Ilvokhin <[email protected]> wrote:
Add thin wrappers around zone lock acquire/release operations. This prepares the code for future tracepoint instrumentation without modifying individual call sites.
Centralizing zone lock operations behind wrappers allows future instrumentation or debugging hooks to be added without touching all users.
No functional change intended. The wrappers are introduced in preparation for subsequent patches and are not yet used.
...
Quoted 9 lines
include/linux/zone_lock.h line 11
Quoted 4 lines
include/linux/zone_lock.h new file +4
-0+static inline void zone_lock_init (struct zone *zone) +{ +spin_lock_init (&zone->lock); +}Please consider renaming zone.lock to something else (
_lockwould be conventional) so that any present and future and out-of-tree unconverted code won't compile.
Thanks for suggestion, Andrew! Makes total sense to me, I'll rename lock to _lock in v3.
PATCH v2 2/4 mm: convert zone lock users to wrappers
In reply to Dmitry IlvokhinReplace direct zone lock acquire/release operations with the newly introduced wrappers.
The changes are purely mechanical substitutions. No functional change intended. Locking semantics and ordering remain unchanged.
The compaction path is left unchanged for now and will be handled separately in the following patch due to additional non-trivial modifications.
--- mm/compaction.c | 25 +++++++++------- mm/memory_hotplug.c | 9 +++--- mm/mm_init.c | 3 +- mm/page_alloc.c | 73 +++++++++++++++++++++++---------------------- mm/page_isolation.c | 19 ++++++------ mm/page_reporting.c | 13 ++++---- mm/show_mem.c | 5 ++-- mm/vmscan.c | 5 ++-- mm/vmstat.c | 9 +++--- 9 files changed, 86 insertions(+), 75 deletions(-)
mm/compaction.c +14 -11
@@ -24,6 +24,7 @@#include <linux/page_owner.h> #include <linux/psi.h> #include <linux/cpuset.h> +#include <linux/zone_lock.h> #include "internal.h" #ifdef CONFIG_COMPACTION
@@ -530,11 +531,14 @@ static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,* Returns true if compaction should abort due to fatal signal pending. * Returns false when compaction can continue. */ -static bool compact_unlock_should_abort (spinlock_t *lock, -unsigned long flags,bool *locked,struct compact_control *cc) + +static bool compact_unlock_should_abort (struct zone *zone, +unsigned long flags, +bool *locked, +struct compact_control *cc) {if (*locked) { -spin_unlock_irqrestore (lock, flags); +zone_unlock_irqrestore (zone, flags); *locked = false; }
@@ -582,9 +586,8 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,* contention, to give chance to IRQs. Abort if fatal signal * pending. */ -if (!(blockpfn %COMPACT_CLUSTER_MAX ) - &&compact_unlock_should_abort (&cc->zone->lock, flags, - &locked, cc)) +if (!(blockpfn %COMPACT_CLUSTER_MAX ) && +compact_unlock_should_abort (cc->zone, flags, &locked, cc))break ; nr_scanned++;
@@ -649,7 +652,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, }if (locked) -spin_unlock_irqrestore (&cc->zone->lock, flags); +zone_unlock_irqrestore (cc->zone, flags);/* * Be careful to not go outside of the pageblock.
@@ -1555,7 +1558,7 @@ static void fast_isolate_freepages(struct compact_control *cc)if (!area->nr_free)continue ; -spin_lock_irqsave (&cc->zone->lock, flags); +zone_lock_irqsave (cc->zone, flags); freelist = &area->free_list[MIGRATE_MOVABLE ];list_for_each_entry_reverse (freepage, freelist, buddy_list) {unsigned long pfn;
@@ -1614,7 +1617,7 @@ static void fast_isolate_freepages(struct compact_control *cc) } } -spin_unlock_irqrestore (&cc->zone->lock, flags); +zone_unlock_irqrestore (cc->zone, flags);/* Skip fast search if enough freepages isolated */ if (cc->nr_freepages >= cc->nr_migratepages)
@@ -1988,7 +1991,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)if (!area->nr_free)continue ; -spin_lock_irqsave (&cc->zone->lock, flags); +zone_lock_irqsave (cc->zone, flags); freelist = &area->free_list[MIGRATE_MOVABLE ];list_for_each_entry (freepage, freelist, buddy_list) {unsigned long free_pfn;
@@ -2021,7 +2024,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)break ; } } -spin_unlock_irqrestore (&cc->zone->lock, flags); +zone_unlock_irqrestore (cc->zone, flags); } cc->total_migrate_scanned += nr_scanned;
mm/memory_hotplug.c +5 -4
@@ -36,6 +36,7 @@#include <linux/rmap.h> #include <linux/module.h> #include <linux/node.h> +#include <linux/zone_lock.h> #include <asm/tlbflush.h>
@@ -1190,9 +1191,9 @@ int online_pages(unsigned long pfn, unsigned long nr_pages,* Fixup the number of isolated pageblocks before marking the sections * onlining, such that undo_isolate_page_range() works correctly. */ -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags); zone->nr_isolate_pageblock += nr_pages / pageblock_nr_pages; -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);/* * If this zone is not populated, then it is not in zonelist.
@@ -2041,9 +2042,9 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,* effectively stale; nobody should be touching them. Fixup the number * of isolated pageblocks, memory onlining will properly revert this. */ -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags); zone->nr_isolate_pageblock -= nr_pages / pageblock_nr_pages; -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);lru_cache_enable ();zone_pcp_enable (zone);
mm/mm_init.c +2 -1
@@ -32,6 +32,7 @@#include <linux/vmstat.h> #include <linux/kexec_handover.h> #include <linux/hugetlb.h> +#include <linux/zone_lock.h> #include "internal.h" #include "slab.h" #include "shuffle.h"
@@ -1425,7 +1426,7 @@ static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx,zone_set_nid (zone, nid); zone->name = zone_names[idx]; zone->zone_pgdat =NODE_DATA (nid); -spin_lock_init (&zone->lock); +zone_lock_init (zone);zone_seqlock_init (zone);zone_pcp_init (zone); }
mm/page_alloc.c +37 -36
266 lines not on this page · raw message
mm/page_isolation.c +10 -9
@@ -10,6 +10,7 @@#include <linux/hugetlb.h> #include <linux/page_owner.h> #include <linux/migrate.h> +#include <linux/zone_lock.h> #include "internal.h" #define CREATE_TRACE_POINTS
@@ -173,7 +174,7 @@ static int set_migratetype_isolate(struct page *page, enum pb_isolate_mode mode,if (PageUnaccepted (page))accept_page (page); -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags);/* * We assume the caller intended to SET migrate type to isolate.
@@ -181,7 +182,7 @@ static int set_migratetype_isolate(struct page *page, enum pb_isolate_mode mode,* set it before us. */ if (is_migrate_isolate_page (page)) { -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);return -EBUSY ; }
@@ -200,15 +201,15 @@ static int set_migratetype_isolate(struct page *page, enum pb_isolate_mode mode, mode);if (!unmovable) {if (!pageblock_isolate_and_move_free_pages (zone, page)) { -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);return -EBUSY ; } zone->nr_isolate_pageblock++; -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);return 0 ; } -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);if (mode ==PB_ISOLATE_MODE_MEM_OFFLINE ) {/* * printk() with zone->lock held will likely trigger a
@@ -229,7 +230,7 @@ static void unset_migratetype_isolate(struct page *page)struct page *buddy; zone =page_zone (page); -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags);if (!is_migrate_isolate_page (page)) goto out;
@@ -280,7 +281,7 @@ static void unset_migratetype_isolate(struct page *page) } zone->nr_isolate_pageblock--; out: -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags); } static inline struct page *
@@ -641,9 +642,9 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,/* Check all pages are free or marked as ISOLATED */ zone =page_zone (page); -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags); pfn =__test_page_isolated_in_pageblock (start_pfn, end_pfn, mode); -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags); ret = pfn < end_pfn ? -EBUSY :0 ;
mm/page_reporting.c +7 -6
@@ -7,6 +7,7 @@#include <linux/module.h> #include <linux/delay.h> #include <linux/scatterlist.h> +#include <linux/zone_lock.h> #include "page_reporting.h" #include "internal.h"
@@ -161,7 +162,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,if (list_empty (list))return err; -spin_lock_irq (&zone->lock); +zone_lock_irq (zone);/* * Limit how many calls we will be making to the page reporting
@@ -219,7 +220,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,list_rotate_to_front (&page->lru, list);/* release lock before waiting on report processing */ -spin_unlock_irq (&zone->lock); +zone_unlock_irq (zone);/* begin processing pages in local list */ err = prdev->report (prdev, sgl,PAGE_REPORTING_CAPACITY );
@@ -231,7 +232,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone, budget--;/* reacquire zone lock and resume processing */ -spin_lock_irq (&zone->lock); +zone_lock_irq (zone);/* flush reported pages from the sg list */ page_reporting_drain (prdev, sgl,PAGE_REPORTING_CAPACITY , !err);
@@ -251,7 +252,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,if (!list_entry_is_head (next, list, lru) && !list_is_first (&next->lru, list))list_rotate_to_front (&next->lru, list); -spin_unlock_irq (&zone->lock); +zone_unlock_irq (zone);return err; }
@@ -296,9 +297,9 @@ page_reporting_process_zone(struct page_reporting_dev_info *prdev, err = prdev->report (prdev, sgl, leftover);/* flush any remaining pages out from the last report */ -spin_lock_irq (&zone->lock); +zone_lock_irq (zone);page_reporting_drain (prdev, sgl, leftover, !err); -spin_unlock_irq (&zone->lock); +zone_unlock_irq (zone); }return err;
mm/show_mem.c +3 -2
@@ -14,6 +14,7 @@#include <linux/mmzone.h> #include <linux/swap.h> #include <linux/vmstat.h> +#include <linux/zone_lock.h> #include "internal.h" #include "swap.h"
@@ -363,7 +364,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_zshow_node (zone);printk (KERN_CONT "%s: " , zone->name); -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags);for (order =0 ; order <NR_PAGE_ORDERS ; order++) {struct free_area *area = &zone->free_area[order];int type;
@@ -377,7 +378,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z types[order] |=1 << type; } } -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags);for (order =0 ; order <NR_PAGE_ORDERS ; order++) {printk (KERN_CONT "%lu*%lukB " , nr[order],K (1UL ) << order);
mm/vmscan.c +3 -2
@@ -58,6 +58,7 @@#include <linux/random.h> #include <linux/mmu_notifier.h> #include <linux/parser.h> +#include <linux/zone_lock.h> #include <asm/tlbflush.h> #include <asm/div64.h>
@@ -7139,9 +7140,9 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)/* Increments are under the zone lock */ zone = pgdat->node_zones + i; -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags); zone->watermark_boost -=min (zone->watermark_boost, zone_boosts[i]); -spin_unlock_irqrestore (&zone->lock, flags); +zone_unlock_irqrestore (zone, flags); }/*
mm/vmstat.c +5 -4
@@ -28,6 +28,7 @@#include <linux/mm_inline.h> #include <linux/page_owner.h> #include <linux/sched/isolation.h> +#include <linux/zone_lock.h> #include "internal.h"
@@ -1535,10 +1536,10 @@ static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,continue ;if (!nolock) -spin_lock_irqsave (&zone->lock, flags); +zone_lock_irqsave (zone, flags);if (!nolock) - spin_unlock_irqrestore(&zone->lock, flags); + zone_unlock_irqrestore(zone, flags); } }#endif
@@ -1603,9 +1604,9 @@ static void pagetypeinfo_showfree_print(struct seq_file *m, } }seq_printf (m,"%s%6lu " , overflow ?">" :"" , freecount); -spin_unlock_irq (&zone->lock); +zone_unlock_irq (zone);cond_resched (); -spin_lock_irq (&zone->lock); +zone_lock_irq (zone); }seq_putc (m,'\n' ); }
Signature · 1 line
2.47.3
PATCH v2 3/4 mm: convert compaction to zone lock wrappers
In reply to Dmitry IlvokhinCompaction uses compact_lock_irqsave(), which currently operates on a raw spinlock_t pointer so that it can be used for both zone->lock and lru_lock. Since zone lock operations are now wrapped, compact_lock_irqsave() can no longer operate directly on a spinlock_t when the lock belongs to a zone.
Introduce struct compact_lock to abstract the underlying lock type. The structure carries a lock type enum and a union holding either a zone pointer or a raw spinlock_t pointer, and dispatches to the appropriate lock/unlock helper.
No functional change intended.
--- mm/compaction.c | 73 +++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 64 insertions(+), 9 deletions(-)
mm/compaction.c +64 -9
@@ -494,6 +494,53 @@ static bool test_and_set_skip(struct compact_control *cc, struct page *page) }#endif /* CONFIG_COMPACTION */ +enum compact_lock_type { +COMPACT_LOCK_ZONE , +COMPACT_LOCK_RAW_SPINLOCK , +}; + +struct compact_lock { +enum compact_lock_type type; +union { +struct zone *zone; +spinlock_t *lock;/* Reference to lru lock */ + }; +}; + +static bool compact_do_trylock_irqsave (struct compact_lock lock, +unsigned long *flags) +{ +if (lock.type ==COMPACT_LOCK_ZONE ) +return zone_trylock_irqsave (lock.zone, *flags); + +return spin_trylock_irqsave (lock.lock, *flags); +} + +static void compact_do_zone_lock_irqsave (struct zone *zone, +unsigned long *flags) +__acquires(zone->lock) +{ +zone_lock_irqsave (zone, *flags); +} + +static void compact_do_raw_lock_irqsave (spinlock_t *lock, +unsigned long *flags) +__acquires (lock) +{ +spin_lock_irqsave (lock, *flags); +} + +static void compact_do_lock_irqsave (struct compact_lock lock, +unsigned long *flags) +{ +if (lock.type ==COMPACT_LOCK_ZONE ) { +compact_do_zone_lock_irqsave (lock.zone, flags); +return ; + } + +compact_do_raw_lock_irqsave (lock.lock, flags); +} +/* * Compaction requires the taking of some coarse locks that are potentially * very heavily contended. For async compaction, trylock and record if the
@@ -503,19 +550,19 @@ static bool test_and_set_skip(struct compact_control *cc, struct page *page)* * Always returns true which makes it easier to track lock state in callers. */ -static bool compact_lock_irqsave (spinlock_t *lock,unsigned long *flags, -struct compact_control *cc) -__acquires (lock) +static bool compact_lock_irqsave (struct compact_lock lock, +unsigned long *flags, +struct compact_control *cc) {/* Track if the lock is contended in async mode */ if (cc->mode ==MIGRATE_ASYNC && !cc->contended) { -if (spin_trylock_irqsave (lock, *flags)) +if (compact_do_trylock_irqsave (lock, flags))return true; cc->contended = true; } -spin_lock_irqsave (lock, *flags); +compact_do_lock_irqsave (lock, flags);return true; }
@@ -531,7 +578,6 @@ static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,* Returns true if compaction should abort due to fatal signal pending. * Returns false when compaction can continue. */ - static bool compact_unlock_should_abort(struct zone *zone, unsigned long flags, bool *locked,
@@ -616,8 +662,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,/* If we already hold the lock, we can skip some rechecking. */ if (!locked) { - locked =compact_lock_irqsave (&cc->zone->lock, - &flags, cc); +struct compact_lock zol = { + .type =COMPACT_LOCK_ZONE , + .zone = cc->zone, + }; + + locked =compact_lock_irqsave (zol, &flags, cc);/* Recheck this is a buddy page under lock */ if (!PageBuddy (page))
@@ -1160,10 +1210,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,/* If we already hold the lock, we can skip some rechecking */ if (lruvec != locked) { +struct compact_lock zol = { + .type =COMPACT_LOCK_RAW_SPINLOCK , + .lock = &lruvec->lru_lock, + }; +if (locked)unlock_page_lruvec_irqrestore (locked, flags); -compact_lock_irqsave (&lruvec->lru_lock, &flags, cc); +compact_lock_irqsave (zol, &flags, cc); locked = lruvec;lruvec_memcg_debug (lruvec, folio);
Signature · 1 line
2.47.3
Andrew Morton
maintainerRe: [PATCH v2 3/4] mm: convert compaction to zone lock wrappers
Quoted 10 lines · On Wed, 25 Feb 2026 14:43:05 +0000 Dmitry Ilvokhin <[email protected]> wrote:
Compaction uses
compact_lock_irqsave(), which currently operates on a rawspinlock_tpointer so that it can be used for bothzone->lockandlru_lock. Since zone lock operations are now wrapped,compact_lock_irqsave()can no longer operate directly on aspinlock_twhen the lock belongs to a zone.Introduce struct
compact_lockto abstract the underlying lock type. The structure carries a lock type enum and a union holding either a zone pointer or a rawspinlock_tpointer, and dispatches to the appropriate lock/unlock helper.
It's regrettable that adds overhead - increased .text, increased instructions.
Thing is, compact_lock_irqsave() has only two callsites. One knows that it's dealing with the zone lock, the other knows that it's dealing with the lruvec lock.
Would it not be simpler and more efficient to copy/paste/edit two versions of compact_lock_irqsave()? A compact_zone_lock_irqsave() and a compact_lruvec_lock_irqsave()?
Re: [PATCH v2 3/4] mm: convert compaction to zone lock wrappers
Quoted 16 lines · Andrew Morton
Quoted 10 lines · On Wed, 25 Feb 2026 14:43:05 +0000 Dmitry Ilvokhin <[email protected]> wrote:
Compaction uses
compact_lock_irqsave(), which currently operates on a rawspinlock_tpointer so that it can be used for bothzone->lockandlru_lock. Since zone lock operations are now wrapped,compact_lock_irqsave()can no longer operate directly on aspinlock_twhen the lock belongs to a zone.Introduce struct
compact_lockto abstract the underlying lock type. The structure carries a lock type enum and a union holding either a zone pointer or a rawspinlock_tpointer, and dispatches to the appropriate lock/unlock helper.It's regrettable that adds overhead - increased .text, increased instructions.
Quoted 8 lines
Thing is,
compact_lock_irqsave()has only two callsites. One knows that it's dealing with the zone lock, the other knows that it's dealing with the lruvec lock.Would it not be simpler and more efficient to copy/paste/edit two versions of
compact_lock_irqsave()? Acompact_zone_lock_irqsave()and acompact_lruvec_lock_irqsave()?
Thanks for the feedback, Andrew.
My initial goal was to reduce code duplication by keeping the logic centralized, but your rationale makes sense. Given that there are only two call sites and both statically know the lock type, splitting the helper avoids unnecessary abstraction.
I'll introduce compact_zone_lock_irqsave() andcompact_lruvec_lock_irqsave() in v3.
PATCH v2 4/4 mm: add tracepoints for zone lock
In reply to Dmitry IlvokhinAdd tracepoint instrumentation to zone lock acquire/release operations via the previously introduced wrappers.
The implementation follows the mmap_lock tracepoint pattern: a lightweight inline helper checks whether the tracepoint is enabled and calls into an out-of-line helper when tracing is active. When CONFIG_TRACING is disabled, helpers compile to empty inline stubs.
The fast path is unaffected when tracing is disabled.
--- MAINTAINERS | 2 + include/linux/zone_lock.h | 64 +++++++++++++++++++++++++++++++- include/trace/events/zone_lock.h | 64 ++++++++++++++++++++++++++++++++ mm/Makefile | 2 +- mm/zone_lock.c | 31 ++++++++++++++++ 5 files changed, 161 insertions(+), 2 deletions(-) create mode 100644 include/trace/events/zone_lock.h create mode 100644 mm/zone_lock.c
MAINTAINERS +2 -0
@@ -16681,6 +16681,7 @@ F: include/linux/ptdump.h F: include/linux/vmpressure.h F: include/linux/vmstat.h F: include/linux/zone_lock.h +F: include/trace/events/zone_lock.h F: kernel/fork.c F: mm/Kconfig F: mm/debug.c
@@ -16700,6 +16701,7 @@ F: mm/sparse.c F: mm/util.c F: mm/vmpressure.c F: mm/vmstat.c +F: mm/zone_lock.c N: include/linux/page[-_]* MEMORY MANAGEMENT - EXECMEM
include/linux/zone_lock.h +63 -1
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include/trace/events/zone_lock.h new file +64 -0
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mm/Makefile +1 -1
@@ -55,7 +55,7 @@ obj-y := filemap.o mempool.o oom_kill.o fadvise.o \ mm_init.o percpu.o slab_common.o \ compaction.o show_mem.o \ interval_tree.o list_lru.o workingset.o \ - debug.o gup.o mmap_lock.o vma_init.o $(mmu-y) + debug.o gup.o mmap_lock.o zone_lock.o vma_init.o $(mmu-y) # Give 'page_alloc' its own module-parameter namespace page-alloc-y := page_alloc.o
mm/zone_lock.c new file +31 -0
@@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0 +#define CREATE_TRACE_POINTS +#include <trace/events/zone_lock.h> + +#include <linux/zone_lock.h> + +EXPORT_TRACEPOINT_SYMBOL (zone_lock_start_locking); +EXPORT_TRACEPOINT_SYMBOL (zone_lock_acquire_returned); +EXPORT_TRACEPOINT_SYMBOL (zone_lock_released); + +#ifdef CONFIG_TRACING + +void __zone_lock_do_trace_start_locking (struct zone *zone) +{ +trace_zone_lock_start_locking (zone); +} +EXPORT_SYMBOL (__zone_lock_do_trace_start_locking); + +void __zone_lock_do_trace_acquire_returned (struct zone *zone,bool success) +{ +trace_zone_lock_acquire_returned (zone, success); +} +EXPORT_SYMBOL (__zone_lock_do_trace_acquire_returned); + +void __zone_lock_do_trace_released (struct zone *zone) +{ +trace_zone_lock_released (zone); +} +EXPORT_SYMBOL (__zone_lock_do_trace_released); + +#endif /* CONFIG_TRACING */
Signature · 1 line
2.47.3