This is a note to let you know that I've just added the patch titled
percpu, x86: don't use PMD_SIZE as embedded atom_size on 32bit
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
percpu-x86-don-t-use-pmd_size-as-embedded-atom_size-on-32bit.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From d5e28005a1d2e67833852f4c9ea8ec206ea3ff85 Mon Sep 17 00:00:00 2001
From: Tejun Heo <[email protected]>
Date: Fri, 27 Apr 2012 10:54:35 -0700
Subject: percpu, x86: don't use PMD_SIZE as embedded atom_size on 32bit
From: Tejun Heo <[email protected]>
commit d5e28005a1d2e67833852f4c9ea8ec206ea3ff85 upstream.
With the embed percpu first chunk allocator, x86 uses either PAGE_SIZE
or PMD_SIZE for atom_size. PMD_SIZE is used when CPU supports PSE so
that percpu areas are aligned to PMD mappings and possibly allow using
PMD mappings in vmalloc areas in the future. Using larger atom_size
doesn't waste actual memory; however, it does require larger vmalloc
space allocation later on for !first chunks.
With reasonably sized vmalloc area, PMD_SIZE shouldn't be a problem
but x86_32 at this point is anything but reasonable in terms of
address space and using larger atom_size reportedly leads to frequent
percpu allocation failures on certain setups.
As there is no reason to not use PMD_SIZE on x86_64 as vmalloc space
is aplenty and most x86_64 configurations support PSE, fix the issue
by always using PMD_SIZE on x86_64 and PAGE_SIZE on x86_32.
v2: drop cpu_has_pse test and make x86_64 always use PMD_SIZE and
x86_32 PAGE_SIZE as suggested by hpa.
Signed-off-by: Tejun Heo <[email protected]>
Reported-by: Yanmin Zhang <[email protected]>
Reported-by: ShuoX Liu <[email protected]>
Acked-by: H. Peter Anvin <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/setup_percpu.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -185,10 +185,22 @@ void __init setup_per_cpu_areas(void)
#endif
rc = -EINVAL;
if (pcpu_chosen_fc != PCPU_FC_PAGE) {
- const size_t atom_size = cpu_has_pse ? PMD_SIZE : PAGE_SIZE;
const size_t dyn_size = PERCPU_MODULE_RESERVE +
PERCPU_DYNAMIC_RESERVE - PERCPU_FIRST_CHUNK_RESERVE;
+ size_t atom_size;
+ /*
+ * On 64bit, use PMD_SIZE for atom_size so that embedded
+ * percpu areas are aligned to PMD. This, in the future,
+ * can also allow using PMD mappings in vmalloc area. Use
+ * PAGE_SIZE on 32bit as vmalloc space is highly contended
+ * and large vmalloc area allocs can easily fail.
+ */
+#ifdef CONFIG_X86_64
+ atom_size = PMD_SIZE;
+#else
+ atom_size = PAGE_SIZE;
+#endif
rc = pcpu_embed_first_chunk(PERCPU_FIRST_CHUNK_RESERVE,
dyn_size, atom_size,
pcpu_cpu_distance,
Patches currently in stable-queue which might be from [email protected] are
queue-3.0/percpu-x86-don-t-use-pmd_size-as-embedded-atom_size-on-32bit.patch
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