Here is a patch that I did recently to reduce the overhead of
clear_page_tables() when using 64k pages on ppc64. It keeps a record
of the maximum address that has been used in each mm_struct. With
this we can kill MM_VM_SIZE.
Andrew - could this go in -mm perhaps?
Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
diff -urN linux-2.6.10/include/asm-ia64/processor.h
g5-64k/include/asm-ia64/processor.h
--- linux-2.6.10/include/asm-ia64/processor.h 2004-11-11 09:57:35.000000000
+1100
+++ g5-64k/include/asm-ia64/processor.h 2005-01-28 13:52:42.000000000 +1100
@@ -43,14 +43,6 @@
#define TASK_SIZE (current->thread.task_size)
/*
- * MM_VM_SIZE(mm) gives the maximum address (plus 1) which may contain a
mapping for
- * address-space MM. Note that with 32-bit tasks, this is still
DEFAULT_TASK_SIZE,
- * because the kernel may have installed helper-mappings above TASK_SIZE. For
example,
- * for x86 emulation, the LDT and GDT are mapped above TASK_SIZE.
- */
-#define MM_VM_SIZE(mm) DEFAULT_TASK_SIZE
-
-/*
* This decides where the kernel will search for a free chunk of vm
* space during mmap's.
*/
diff -urN linux-2.6.10/include/linux/mm.h g5-64k/include/linux/mm.h
--- linux-2.6.10/include/linux/mm.h 2004-11-25 17:42:43.000000000 +1100
+++ g5-64k/include/linux/mm.h 2005-01-28 13:52:14.848021352 +1100
@@ -37,10 +37,6 @@
#include <asm/processor.h>
#include <asm/atomic.h>
-#ifndef MM_VM_SIZE
-#define MM_VM_SIZE(mm) TASK_SIZE
-#endif
-
#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
/*
diff -urN linux-2.6.10/include/linux/sched.h g5-64k/include/linux/sched.h
--- linux-2.6.10/include/linux/sched.h 2004-12-03 18:31:57.000000000 +1100
+++ g5-64k/include/linux/sched.h 2004-12-26 16:21:37.000000000 +1100
@@ -228,6 +228,7 @@
unsigned long arg_start, arg_end, env_start, env_end;
unsigned long rss, anon_rss, total_vm, locked_vm, shared_vm;
unsigned long exec_vm, stack_vm, reserved_vm, def_flags, nr_ptes;
+ unsigned long max_addr;
unsigned long saved_auxv[42]; /* for /proc/PID/auxv */
diff -urN linux-2.6.10/mm/mmap.c g5-64k/mm/mmap.c
--- linux-2.6.10/mm/mmap.c 2004-12-13 21:47:27.000000000 +1100
+++ g5-64k/mm/mmap.c 2005-01-28 13:47:33.000000000 +1100
@@ -317,6 +317,8 @@
if (mapping)
spin_unlock(&mapping->i_mmap_lock);
+ if (vma->vm_end && vma->vm_end - 1 > mm->max_addr)
+ mm->max_addr = vma->vm_end - 1;
mm->map_count++;
validate_mm(mm);
}
@@ -496,6 +498,8 @@
}
}
+ if (vma->vm_end && vma->vm_end - 1 > mm->max_addr)
+ mm->max_addr = vma->vm_end - 1;
validate_mm(mm);
}
@@ -1832,6 +1836,7 @@
struct mmu_gather *tlb;
struct vm_area_struct *vma;
unsigned long nr_accounted = 0;
+ int nr_pgds;
lru_add_drain();
@@ -1844,8 +1849,10 @@
~0UL, &nr_accounted, NULL);
vm_unacct_memory(nr_accounted);
BUG_ON(mm->map_count); /* This is just debugging */
- clear_page_tables(tlb, FIRST_USER_PGD_NR, USER_PTRS_PER_PGD);
- tlb_finish_mmu(tlb, 0, MM_VM_SIZE(mm));
+ nr_pgds = pgd_index(mm->max_addr) - FIRST_USER_PGD_NR + 1;
+ if (nr_pgds > 0)
+ clear_page_tables(tlb, FIRST_USER_PGD_NR, nr_pgds);
+ tlb_finish_mmu(tlb, 0, mm->max_addr + 1);
vma = mm->mmap;
mm->mmap = mm->mmap_cache = NULL;
