[PATCH] Drop VFS cache when there is not enough free memory to allocate

[Aubrey . Li]

Signed-off-by: Aubrey.Li <aubrey.li@xxxxxxxxxx>
---
 mm/page_alloc.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bf2f6cf..62559fd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1039,6 +1039,11 @@ restart:
        if (page)
                goto got_pg;

+#if defined(CONFIG_EMBEDDED) && !defined(CONFIG_MMU)
+       drop_pagecache();
+       drop_slab();
+#endif
+
        /* This allocation should allow future memory freeing. */

        if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
--
1.4.2
========================================

The patch drop the page cache and slab and then give a new chance to
get more free pages. Applied this patch, my test application can
allocate memory sucessfully and drop the cache and slab as well. See
below:
================================
root:/mnt> ./t
Alloc 8 MB !
alloc successful
root:/mnt> cat /proc/meminfo
MemTotal:        54196 kB
MemFree:         43684 kB
Buffers:            36 kB
Cached:            440 kB
SwapCached:          0 kB
Active:             32 kB
Inactive:          432 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:        54196 kB
LowFree:         43684 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:               8 kB
Writeback:           0 kB
AnonPages:           0 kB
Mapped:              0 kB
Slab:             9812 kB
PageTables:          0 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:     27096 kB
Committed_AS:        0 kB
VmallocTotal:        0 kB
VmallocUsed:         0 kB
VmallocChunk:        0 kB
=============================

I know performance is important for linux, and VFS cache obviously
improve the performance when implement file operation. But for
embedded system, we'll try our best to make the application executable
rather than hanging system to guarantee the system performance.

Any suggestions and solutions are really appreciated!

Thanks,
-Aubrey

------=_Part_67747_12127413.1164181866877
Content-Type: text/plain; name="0001-Drop-VFS-cache-when-there-is-not-enough-free-memory-to-allocate.txt"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="0001-Drop-VFS-cache-when-there-is-not-enough-free-memory-to-allocate.txt"
X-Attachment-Id: f_eutggk2u
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==
------=_Part_67747_12127413.1164181866877--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/