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Date: Mon, 8 Oct 2012 17:41:14 +0200
From: Rabin Vincent <rabin@....in>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: CMA and zone watermarks
It appears that when CMA is enabled, the zone watermarks are not properly
respected, leading to for example GFP_NOWAIT allocations getting access to the
high pools.
I ran the following test code which simply allocates pages with GFP_NOWAIT
until it fails, and then tries GFP_ATOMIC. Without CMA, the GFP_ATOMIC
allocation succeeds, with CMA, it fails too.
Logs attached (includes my patch which prints the migration type in the failure
message http://marc.info/?l=linux-mm&m=134971041701306&w=2), taken on 3.6
kernel.
Thanks.
diff --git a/arch/arm/mach-ux500/board-mop500.c
b/arch/arm/mach-ux500/board-mop500.c
index a534d88..b98d0df 100644
--- a/arch/arm/mach-ux500/board-mop500.c
+++ b/arch/arm/mach-ux500/board-mop500.c
@@ -854,3 +854,25 @@ DT_MACHINE_START(U8500_DT, "ST-Ericsson U8500
platform (Device Tree Support)")
.dt_compat = u8500_dt_board_compat,
MACHINE_END
#endif
+
+static int __init late(void)
+{
+ while (1) {
+ void *p;
+
+ p = alloc_page(GFP_NOWAIT);
+ if (!p) {
+ pr_err("GFP_NOWAIT failed, checking GFP_ATOMIC");
+
+ p = alloc_page(GFP_ATOMIC);
+ if (!p)
+ panic("GFP_ATOMIC failed too, fail!");
+
+ panic("GFP_ATOMIC OK, all good\n");
+ }
+
+ }
+
+ return 0;
+}
+late_initcall(late);
Download attachment "cmalog.txt.gz" of type "application/x-gzip" (6122 bytes)
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