[PATCH 04/19] mm: debug page reclaim
From: Wu Fengguang
Date: Fri Nov 25 2005 - 10:06:05 EST
Show the detailed steps of early/direct/kswapd page reclaim.
To enable the printk traces:
# echo y > /debug/debug_page_reclaim
Sample lines:
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-31, age 1248, hot+cold+free pages 92563+25703+860
reclaim zone2 from kswapd for watermark, prio 11, scan-reclaimed 33-32, age 1253, hot+cold+free pages 92547+25688+892
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1258, hot+cold+free pages 92547+25656+924
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-29, age 1262, hot+cold+free pages 92532+25639+924
reclaim zone2 from kswapd for watermark, prio 11, scan-reclaimed 33-28, age 1269, hot+cold+free pages 92531+25611+956
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-31, age 1274, hot+cold+free pages 92535+25579+988
reclaim zone2 from kswapd for watermark, prio 11, scan-reclaimed 33-29, age 1278, hot+cold+free pages 92518+25565+1020
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-29, age 1282, hot+cold+free pages 92507+25547+1052
reclaim zone2 from kswapd for aging, prio 11, scan-reclaimed 33-27, age 1287, hot+cold+free pages 92506+25519+1084
reclaim zone2 from direct for aging, prio 12, scan-reclaimed 33-29, age 1292, hot+cold+free pages 92505+25494+1116
reclaim zone2 from direct for aging, prio 11, scan-reclaimed 33-32, age 1297, hot+cold+free pages 92506+25464+1148
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1302, hot+cold+free pages 92506+25746+860
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1307, hot+cold+free pages 92488+25732+892
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1312, hot+cold+free pages 92488+25700+924
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1316, hot+cold+free pages 92481+25675+956
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1322, hot+cold+free pages 92481+25643+988
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1326, hot+cold+free pages 92474+25618+1020
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1331, hot+cold+free pages 92474+25586+1052
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 33-32, age 1336, hot+cold+free pages 92474+25554+1084
reclaim zone2 from direct for aging, prio 12, scan-reclaimed 33-32, age 1341, hot+cold+free pages 92474+25522+1116
reclaim zone2 from direct for aging, prio 12, scan-reclaimed 33-32, age 1347, hot+cold+free pages 92470+25744+892
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-32, age 1352, hot+cold+free pages 92463+25712+924
reclaim zone2 from kswapd for watermark, prio 12, scan-reclaimed 33-25, age 1357, hot+cold+free pages 92462+25681+956
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 75 insertions(+), 15 deletions(-)
--- linux-2.6.15-rc2-mm1.orig/mm/vmscan.c
+++ linux-2.6.15-rc2-mm1/mm/vmscan.c
@@ -38,6 +38,7 @@
#include <asm/div64.h>
#include <linux/swapops.h>
+#include <linux/debugfs.h>
/* possible outcome of pageout() */
typedef enum {
@@ -72,10 +73,7 @@ struct scan_control {
/* This context's GFP mask */
gfp_t gfp_mask;
- int may_writepage;
-
- /* Can pages be swapped as part of reclaim? */
- int may_swap;
+ unsigned long flags;
/* This context's SWAP_CLUSTER_MAX. If freeing memory for
* suspend, we effectively ignore SWAP_CLUSTER_MAX.
@@ -84,6 +82,59 @@ struct scan_control {
int swap_cluster_max;
};
+#define SC_RECLAIM_FROM_KSWAPD 0x01
+#define SC_RECLAIM_FROM_DIRECT 0x02
+#define SC_RECLAIM_FROM_EARLY 0x04
+#define SC_RECLAIM_FOR_WATERMARK 0x10
+#define SC_RECLAIM_FOR_AGING 0x20
+#define SC_RECLAIM_MASK 0xFF
+
+#define SC_MAY_WRITEPAGE 0x100
+#define SC_MAY_SWAP 0x200 /* Can pages be swapped as part of reclaim? */
+
+#ifdef CONFIG_DEBUG_FS
+static u32 debug_page_reclaim;
+
+static inline void debug_reclaim(struct scan_control *sc, unsigned long flags)
+{
+ sc->flags = (sc->flags & ~SC_RECLAIM_MASK) | flags;
+}
+
+static inline void debug_reclaim_report(struct scan_control *sc, struct zone *z)
+{
+ if (!debug_page_reclaim)
+ return;
+
+ printk(KERN_DEBUG "reclaim zone%d from %s for %s, "
+ "prio %d, scan-reclaimed %lu-%lu, age %lu, "
+ "hot+cold+free pages %lu+%lu+%lu\n",
+ zone_idx(z),
+ (sc->flags & SC_RECLAIM_FROM_KSWAPD) ? "kswapd" :
+ ((sc->flags & SC_RECLAIM_FROM_DIRECT) ? "direct" :
+ "early"),
+ (sc->flags & SC_RECLAIM_FOR_AGING) ?
+ "aging" : "watermark",
+ sc->priority, sc->nr_scanned, sc->nr_reclaimed,
+ z->page_age, z->nr_active, z->nr_inactive, z->free_pages);
+}
+
+static inline void debug_reclaim_init(void)
+{
+ debugfs_create_bool("debug_page_reclaim", 0644, NULL,
+ &debug_page_reclaim);
+}
+#else
+static inline void debug_reclaim(struct scan_control *sc, int flags)
+{
+}
+static inline void debug_reclaim_report(struct scan_control *sc, struct zone *z)
+{
+}
+static inline void debug_reclaim_init(void)
+{
+}
+#endif
+
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
#ifdef ARCH_HAS_PREFETCH
@@ -499,7 +550,7 @@ static int shrink_list(struct list_head
* Try to allocate it some swap space here.
*/
if (PageAnon(page) && !PageSwapCache(page)) {
- if (!sc->may_swap)
+ if (!(sc->flags & SC_MAY_SWAP))
goto keep_locked;
if (!add_to_swap(page, GFP_ATOMIC))
goto activate_locked;
@@ -530,7 +581,7 @@ static int shrink_list(struct list_head
goto keep_locked;
if (!may_enter_fs)
goto keep_locked;
- if (laptop_mode && !sc->may_writepage)
+ if (laptop_mode && !(sc->flags & SC_MAY_WRITEPAGE))
goto keep_locked;
/* Page is dirty, try to write it out here */
@@ -939,6 +990,7 @@ static void shrink_cache(struct zone *zo
mod_page_state(kswapd_steal, nr_freed);
mod_page_state_zone(zone, pgsteal, nr_freed);
sc->nr_to_reclaim -= nr_freed;
+ debug_reclaim_report(sc, zone);
spin_lock_irq(&zone->lru_lock);
/*
@@ -1216,11 +1268,14 @@ shrink_caches(struct zone **zones, struc
continue;
}
+ debug_reclaim(sc, SC_RECLAIM_FROM_DIRECT);
shrink_zone(zone, sc);
}
- if (z)
+ if (z) {
+ debug_reclaim(sc, SC_RECLAIM_FROM_DIRECT|SC_RECLAIM_FOR_AGING);
shrink_zone(z, sc);
+ }
}
/*
@@ -1248,8 +1303,7 @@ int try_to_free_pages(struct zone **zone
delay_prefetch();
sc.gfp_mask = gfp_mask;
- sc.may_writepage = 0;
- sc.may_swap = 1;
+ sc.flags = SC_MAY_SWAP;
inc_page_state(allocstall);
@@ -1290,7 +1344,7 @@ int try_to_free_pages(struct zone **zone
*/
if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
wakeup_pdflush(laptop_mode ? 0 : total_scanned);
- sc.may_writepage = 1;
+ sc.flags |= SC_MAY_WRITEPAGE;
}
/* Take a nap, wait for some writeback to complete */
@@ -1365,8 +1419,7 @@ loop_again:
total_scanned = 0;
total_reclaimed = 0;
sc.gfp_mask = GFP_KERNEL;
- sc.may_writepage = 0;
- sc.may_swap = 1;
+ sc.flags = SC_MAY_SWAP;
sc.nr_mapped = read_page_state(nr_mapped);
inc_page_state(pageoutrun);
@@ -1395,10 +1448,16 @@ loop_again:
if (!zone_watermark_ok(zone, order,
zone->pages_high,
0, 0)) {
+ debug_reclaim(&sc,
+ SC_RECLAIM_FROM_KSWAPD|
+ SC_RECLAIM_FOR_WATERMARK);
all_zones_ok = 0;
} else if (zone == youngest_zone &&
pages_more_aged(oldest_zone,
youngest_zone)) {
+ debug_reclaim(&sc,
+ SC_RECLAIM_FROM_KSWAPD|
+ SC_RECLAIM_FOR_AGING);
/* if (priority > DEF_PRIORITY - 2) */
/* all_zones_ok = 0; */
} else
@@ -1433,7 +1492,7 @@ loop_again:
*/
if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
total_scanned > total_reclaimed+total_reclaimed/2)
- sc.may_writepage = 1;
+ sc.flags |= SC_MAY_WRITEPAGE;
if (nr_pages && to_free > total_reclaimed)
continue; /* swsusp: need to do more work */
@@ -1623,6 +1682,7 @@ static int __init kswapd_init(void)
= find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
total_memory = nr_free_pagecache_pages();
hotcpu_notifier(cpu_callback, 0);
+ debug_reclaim_init();
return 0;
}
@@ -1645,8 +1705,7 @@ int zone_reclaim(struct zone *zone, gfp_
return 0;
sc.gfp_mask = gfp_mask;
- sc.may_writepage = 0;
- sc.may_swap = 0;
+ sc.flags = 0;
sc.nr_mapped = read_page_state(nr_mapped);
sc.nr_scanned = 0;
sc.nr_reclaimed = 0;
@@ -1662,6 +1721,7 @@ int zone_reclaim(struct zone *zone, gfp_
if (atomic_read(&zone->reclaim_in_progress) > 0)
goto out;
+ debug_reclaim(&sc, SC_RECLAIM_FROM_EARLY);
shrink_zone(zone, &sc);
total_reclaimed = sc.nr_reclaimed;
--
-
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