Re: quicklists confuse meminfo

From: KOSAKI Motohiro
Date: Sun Mar 09 2008 - 08:49:32 EST

Hi

> > IMHO we need shrink pgtable cache mecanism.
>
> ouch! Could you try the patch below? How large is the quicklist cache
> with this applied?

I porting to IA64, applied, and tested.
but no change behavior.

because quicklist.c::max_pages() formula is strange.
my freememory is about 5GB, thus this function calculate 5GB/16 ~= 300MB,
my machine has 8cpu, thus 300MB x 8 ~= 2.5GB consume at worst case.
(because this variable is per cpu variable)

IMHO FRACTION_OF_NODE_MEM(16) is too small.

after change FRACTION_OF_NODE_MEM to 256,
i got following result.


---------------------------------------------------
MemTotal: 7683328 kB
MemFree: 5904704 kB
Buffers: 28672 kB
Cached: 168384 kB
SwapCached: 1344 kB
Active: 173376 kB
Inactive: 126016 kB
SwapTotal: 2031488 kB
SwapFree: 2030144 kB
Dirty: 64 kB
Writeback: 0 kB
AnonPages: 101120 kB
Mapped: 34496 kB
Slab: 1332608 kB
SReclaimable: 21824 kB
SUnreclaim: 1310784 kB
PageTables: 12480 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 5873152 kB
Committed_AS: 383744 kB
VmallocTotal: 17592177655808 kB
VmallocUsed: 28864 kB
VmallocChunk: 17592177623040 kB
Quicklists: 61888 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 262144 kB
-----------------------------------------------

the following patch is explain to my shrink plan and change to
FRACTION_OF_NODE_MEM value.
of cource, this is only base of discussion.

I don't tested performance regression test yet.




Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>

---
fs/drop_caches.c | 3 +++
include/asm-ia64/pgalloc.h | 9 ++++++++-
include/linux/quicklist.h | 7 +++++++
mm/quicklist.c | 2 +-
mm/vmscan.c | 8 ++++++++
5 files changed, 27 insertions(+), 2 deletions(-)

Index: b/fs/drop_caches.c
===================================================================
--- a/fs/drop_caches.c 2008-03-09 16:04:14.000000000 +0900
+++ b/fs/drop_caches.c 2008-03-09 20:38:44.000000000 +0900
@@ -8,6 +8,7 @@
#include <linux/writeback.h>
#include <linux/sysctl.h>
#include <linux/gfp.h>
+#include <asm/pgalloc.h>

/* A global variable is a bit ugly, but it keeps the code simple */
int sysctl_drop_caches;
@@ -63,6 +64,8 @@ int drop_caches_sysctl_handler(ctl_table
drop_pagecache();
if (sysctl_drop_caches & 2)
drop_slab();
+ if (sysctl_drop_caches & 4)
+ drop_pgtable_cache();
}
return 0;
}
Index: b/include/linux/quicklist.h
===================================================================
--- a/include/linux/quicklist.h 2008-03-09 19:45:58.000000000 +0900
+++ b/include/linux/quicklist.h 2008-03-09 21:49:07.000000000 +0900
@@ -87,6 +87,13 @@ static inline unsigned long quicklist_to
return 0;
}

+static inline void quicklist_trim(int nr, void (*dtor)(void *),
+ unsigned long min_pages,
+ unsigned long max_free)
+{
+}
+
+
#endif

#endif /* LINUX_QUICKLIST_H */
Index: b/mm/quicklist.c
===================================================================
--- a/mm/quicklist.c 2008-03-09 16:04:53.000000000 +0900
+++ b/mm/quicklist.c 2008-03-09 21:35:18.000000000 +0900
@@ -21,7 +21,7 @@

DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];

-#define FRACTION_OF_NODE_MEM 16
+#define FRACTION_OF_NODE_MEM 256

static unsigned long max_pages(unsigned long min_pages)
{
Index: b/include/asm-ia64/pgalloc.h
===================================================================
--- a/include/asm-ia64/pgalloc.h 2008-03-09 21:53:14.000000000 +0900
+++ b/include/asm-ia64/pgalloc.h 2008-03-09 21:53:53.000000000 +0900
@@ -114,9 +114,16 @@ static inline void pte_free_kernel(struc

static inline void check_pgt_cache(void)
{
- quicklist_trim(0, NULL, 25, 16);
+ quicklist_trim(0, NULL, 25, 1024);
}

#define __pte_free_tlb(tlb, pte) pte_free((tlb)->mm, pte)

+#define HAVE_ARCH_DROP_PGTABLE_CACHE
+static inline void drop_pgtable_cache(void)
+{
+ quicklist_trim(0, NULL, 25, ULONG_MAX);
+}
+
+
#endif /* _ASM_IA64_PGALLOC_H */
Index: b/mm/vmscan.c
===================================================================
--- a/mm/vmscan.c 2008-03-09 19:42:47.000000000 +0900
+++ b/mm/vmscan.c 2008-03-09 20:45:24.000000000 +0900
@@ -42,6 +42,7 @@

#include <asm/tlbflush.h>
#include <asm/div64.h>
+#include <asm/pgalloc.h>

#include <linux/swapops.h>

@@ -1362,6 +1363,7 @@ static unsigned long do_try_to_free_page
* over limit cgroups
*/
if (scan_global_lru(sc)) {
+ drop_pgtable_cache();
shrink_slab(sc->nr_scanned, gfp_mask, lru_pages);
if (reclaim_state) {
nr_reclaimed += reclaim_state->reclaimed_slab;
@@ -1589,6 +1591,7 @@ loop_again:
if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
end_zone, 0))
nr_reclaimed += shrink_zone(priority, zone, &sc);
+ drop_pgtable_cache();
reclaim_state->reclaimed_slab = 0;
nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
lru_pages);
@@ -1831,6 +1834,7 @@ unsigned long shrink_all_memory(unsigned
nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
/* If slab caches are huge, it's better to hit them first */
while (nr_slab >= lru_pages) {
+ drop_pgtable_cache();
reclaim_state.reclaimed_slab = 0;
shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
if (!reclaim_state.reclaimed_slab)
@@ -1868,6 +1872,7 @@ unsigned long shrink_all_memory(unsigned
if (ret >= nr_pages)
goto out;

+ drop_pgtable_cache();
reclaim_state.reclaimed_slab = 0;
shrink_slab(sc.nr_scanned, sc.gfp_mask,
count_lru_pages());
@@ -1880,6 +1885,7 @@ unsigned long shrink_all_memory(unsigned
}
}

+ drop_pgtable_cache();
/*
* If ret = 0, we could not shrink LRUs, but there may be something
* in slab caches
@@ -2038,6 +2044,8 @@ static int __zone_reclaim(struct zone *z
} while (priority >= 0 && nr_reclaimed < nr_pages);
}

+ drop_pgtable_cache();
+
slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
if (slab_reclaimable > zone->min_slab_pages) {
/*

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