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Subject[PATCH 11/12] mm: add page reclaim debug traces
Show the detailed steps of direct/kswapd page reclaim.

To enable the printk traces:
# echo y > /debug/debug_page_reclaim
Sample lines:

reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 32-32, age 2626, active to scan 6542, hot+cold+free pages 8842+283558+352
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2626, active to scan 8018, hot+cold+free pages 1693+200036+10360
reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 64-64, age 2627, active to scan 7564, hot+cold+free pages 8842+283526+384
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2627, active to scan 8296, hot+cold+free pages 1693+200018+10360
reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 64-63, age 2628, active to scan 8587, hot+cold+free pages 8843+283495+416
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2628, active to scan 8574, hot+cold+free pages 1693+200014+10392
reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 64-63, age 2628, active to scan 9610, hot+cold+free pages 8844+283465+448
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2628, active to scan 8852, hot+cold+free pages 1693+199996+10424
reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 64-64, age 2629, active to scan 10633, hot+cold+free pages 8844+283433+480
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2629, active to scan 9130, hot+cold+free pages 1693+199992+10456
reclaim zone3 from kswapd for watermark, prio 12, scan-reclaimed 64-64, age 2630, active to scan 11656, hot+cold+free pages 8844+283401+512
reclaim zone2 from kswapd for aging, prio 12, scan-reclaimed 32-32, age 2630, active to scan 9408, hot+cold+free pages 1693+199974+10488
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---

mm/vmscan.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 69 insertions(+), 1 deletion(-)
--- linux.orig/mm/vmscan.c
+++ linux/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 {
@@ -78,6 +79,62 @@ struct scan_control {
#define SC_MAY_WRITEPAGE 0x1
#define SC_MAY_SWAP 0x2 /* Can pages be swapped as part of reclaim? */

+#define SC_RECLAIM_FROM_KSWAPD 0x10
+#define SC_RECLAIM_FROM_DIRECT 0x20
+#define SC_RECLAIM_FOR_WATERMARK 0x40
+#define SC_RECLAIM_FOR_AGING 0x80
+#define SC_RECLAIM_MASK 0xF0
+
+#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, "
+ "active to scan %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_scan_active,
+ z->nr_active, z->nr_inactive, z->free_pages);
+
+ if (atomic_read(&z->reclaim_in_progress))
+ printk(KERN_WARNING "reclaim_in_progress=%d\n",
+ atomic_read(&z->reclaim_in_progress));
+}
+
+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
@@ -1141,6 +1198,7 @@ shrink_zone(struct zone *zone, struct sc

atomic_dec(&zone->reclaim_in_progress);

+ debug_reclaim_report(sc, zone);
throttle_vm_writeout();
}

@@ -1205,11 +1263,14 @@ 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);
+ }
}

/*
@@ -1386,10 +1447,16 @@ 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);
} else
continue;
}
@@ -1611,6 +1678,7 @@ 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;
}

--
-
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