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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 /Documentation
parente59a1bb2fdfb745c685f5b40ffbed126331d3223 (diff)
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 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 08def8deb5f..ecad946920d 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1882,6 +1882,12 @@ and is between 256 and 4096 characters. It is defined in the file
Format: { 0 | 1 }
See arch/parisc/kernel/pdc_chassis.c
+ percpu_alloc= [X86] Select which percpu first chunk allocator to use.
+ Allowed values are one of "lpage", "embed" and "4k".
+ See comments in arch/x86/kernel/setup_percpu.c for
+ details on each allocator. This parameter is primarily
+ for debugging and performance comparison.
+
pf. [PARIDE]
See Documentation/blockdev/paride.txt.