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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2008-04-30 15:41:48 +1000
committerPaul Mackerras <paulus@samba.org>2008-05-15 20:49:25 +1000
commitcec08e7a948326b01555be6311480aa08e637de2 (patch)
treea08e1d91c9a0c5eaa4e81036a3d7f992b2de1745 /arch/powerpc/mm/slb_low.S
parent08fcf1d61193d7b7779aa6d7388535e26e064a0b (diff)
[POWERPC] vmemmap fixes to use smaller pages
This changes vmemmap to use a different region (region 0xf) of the address space, and to configure the page size of that region dynamically at boot. The problem with the current approach of always using 16M pages is that it's not well suited to machines that have small amounts of memory such as small partitions on pseries, or PS3's. In fact, on the PS3, failure to allocate the 16M page backing vmmemmap tends to prevent hotplugging the HV's "additional" memory, thus limiting the available memory even more, from my experience down to something like 80M total, which makes it really not very useable. The logic used by my match to choose the vmemmap page size is: - If 16M pages are available and there's 1G or more RAM at boot, use that size. - Else if 64K pages are available, use that - Else use 4K pages I've tested on a POWER6 (16M pages) and on an iSeries POWER3 (4K pages) and it seems to work fine. Note that I intend to change the way we organize the kernel regions & SLBs so the actual region will change from 0xf back to something else at one point, as I simplify the SLB miss handler, but that will be for a later patch. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/mm/slb_low.S')
-rw-r--r--arch/powerpc/mm/slb_low.S16
1 files changed, 13 insertions, 3 deletions
diff --git a/arch/powerpc/mm/slb_low.S b/arch/powerpc/mm/slb_low.S
index 657f6b37e9d..bc44dc4b5c6 100644
--- a/arch/powerpc/mm/slb_low.S
+++ b/arch/powerpc/mm/slb_low.S
@@ -47,8 +47,7 @@ _GLOBAL(slb_allocate_realmode)
* it to VSID 0, which is reserved as a bad VSID - one which
* will never have any pages in it. */
- /* Check if hitting the linear mapping of the vmalloc/ioremap
- * kernel space
+ /* Check if hitting the linear mapping or some other kernel space
*/
bne cr7,1f
@@ -62,7 +61,18 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFCLR(CPU_FTR_1T_SEGMENT)
b slb_finish_load_1T
-1: /* vmalloc/ioremap mapping encoding bits, the "li" instructions below
+1:
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ /* Check virtual memmap region. To be patches at kernel boot */
+ cmpldi cr0,r9,0xf
+ bne 1f
+_GLOBAL(slb_miss_kernel_load_vmemmap)
+ li r11,0
+ b 6f
+1:
+#endif /* CONFIG_SPARSEMEM_VMEMMAP */
+
+ /* vmalloc/ioremap mapping encoding bits, the "li" instructions below
* will be patched by the kernel at boot
*/
BEGIN_FTR_SECTION