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authorTejun Heo <tj@kernel.org>2009-06-22 11:56:24 +0900
committerTejun Heo <tj@kernel.org>2009-06-22 11:56:24 +0900
commitfa8a7094ba1679b4b9b443e0ac9f5e046c79ee8d (patch)
treecda9df47b1a84581685d8f4e0cd8ce66cac1d234 /mm/percpu.c
parente59a1bb2fdfb745c685f5b40ffbed126331d3223 (diff)
downloadvexpress-lsk-fa8a7094ba1679b4b9b443e0ac9f5e046c79ee8d.tar.gz
x86: implement percpu_alloc kernel parameter
According to Andi, it isn't clear whether lpage allocator is worth the trouble as there are many processors where PMD TLB is far scarcer than PTE TLB. The advantage or disadvantage probably depends on the actual size of percpu area and specific processor. As performance degradation due to TLB pressure tends to be highly workload specific and subtle, it is difficult to decide which way to go without more data. This patch implements percpu_alloc kernel parameter to allow selecting which first chunk allocator to use to ease debugging and testing. While at it, make sure all the failure paths report why something failed to help determining why certain allocator isn't working. Also, kill the "Great future plan" comment which had already been realized quite some time ago. [ Impact: allow explicit percpu first chunk allocator selection ] Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jan Beulich <JBeulich@novell.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'mm/percpu.c')
-rw-r--r--mm/percpu.c13
1 files changed, 9 insertions, 4 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index d06f4748271..b70f2acd885 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1233,6 +1233,7 @@ static struct page * __init pcpue_get_page(unsigned int cpu, int pageno)
ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
ssize_t dyn_size, ssize_t unit_size)
{
+ size_t chunk_size;
unsigned int cpu;
/* determine parameters and allocate */
@@ -1247,11 +1248,15 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
} else
pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
- pcpue_ptr = __alloc_bootmem_nopanic(
- num_possible_cpus() * pcpue_unit_size,
- PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
- if (!pcpue_ptr)
+ chunk_size = pcpue_unit_size * num_possible_cpus();
+
+ pcpue_ptr = __alloc_bootmem_nopanic(chunk_size, PAGE_SIZE,
+ __pa(MAX_DMA_ADDRESS));
+ if (!pcpue_ptr) {
+ pr_warning("PERCPU: failed to allocate %zu bytes for "
+ "embedding\n", chunk_size);
return -ENOMEM;
+ }
/* return the leftover and copy */
for_each_possible_cpu(cpu) {