diff options
| author | Hugh Dickins <hugh@veritas.com> | 2005-11-23 13:37:37 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-23 16:08:38 -0800 |
| commit | 7b6ac9dffe6f4dd8776908b234ac1410ed15f112 (patch) | |
| tree | 1e30fde299519eb964899be79560599e04a32a66 /mm/Kconfig | |
| parent | c101e77301877086e6f977fcfb140d1cbbe23fd5 (diff) | |
| download | lwn-7b6ac9dffe6f4dd8776908b234ac1410ed15f112.tar.gz lwn-7b6ac9dffe6f4dd8776908b234ac1410ed15f112.zip | |
[PATCH] mm: update split ptlock Kconfig
Closer attention to the arithmetic shows that neither ppc64 nor sparc really
uses one page for multiple page tables: how on earth could they, while
pte_alloc_one returns just a struct page pointer, with no offset?
Well, arm26 manages it by returning a pte_t pointer cast to a struct page
pointer, harumph, then compensating in its pmd_populate. But arm26 is never
SMP, so it's not a problem for split ptlock either.
And the PA-RISC situation has been recently improved: CONFIG_PA20 works
without the 16-byte alignment which inflated its spinlock_t. But the current
union of spinlock_t with private does make the 7xxx struct page significantly
larger, even without debug, so disable its split ptlock.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/Kconfig')
| -rw-r--r-- | mm/Kconfig | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index ae9ce6b73e8a..21eb51d4da8f 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -125,12 +125,10 @@ comment "Memory hotplug is currently incompatible with Software Suspend" # space can be handled with less contention: split it at this NR_CPUS. # Default to 4 for wider testing, though 8 might be more appropriate. # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. -# PA-RISC's debug spinlock_t is too large for the 32-bit struct page. -# ARM26 and SPARC32 and PPC64 may use one page for multiple page tables. +# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. # config SPLIT_PTLOCK_CPUS int default "4096" if ARM && !CPU_CACHE_VIPT - default "4096" if PARISC && DEBUG_SPINLOCK && !64BIT - default "4096" if ARM26 || SPARC32 || PPC64 + default "4096" if PARISC && !PA20 default "4" |