Hi,
after a weekend research i am a bit stuck in my understanding of the
R3000 swapping problems
When changing
Index: include/asm-mips/pgtable.h
===================================================================
RCS file: /cvs/linux/include/asm-mips/pgtable.h,v
retrieving revision 1.48
diff -u -r1.48 pgtable.h
--- include/asm-mips/pgtable.h 2000/12/03 15:30:52 1.48
+++ include/asm-mips/pgtable.h 2001/01/28 16:08:17
@@ -457,8 +457,8 @@
unsigned long address, pte_t pte);
#define SWP_TYPE(x) (((x).val >> 1) & 0x3f)
-#define SWP_OFFSET(x) ((x).val >> 8)
-#define SWP_ENTRY(type,offset) ((swp_entry_t) { ((type) << 1) | ((offset) << 8) })
+#define SWP_OFFSET(x) ((x).val >> 10)
+#define SWP_ENTRY(type,offset) ((swp_entry_t) { ((type) << 1) | ((offset) << 10) })
#define pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define swp_entry_to_pte(x) ((pte_t) { (x).val })
The R3k machine (Decstation 5000/120) does survive swapping. The
idea is that the bits 9 & 10 on the R3k are
#define _PAGE_VALID (1<<9)
#define _PAGE_SILENT_READ (1<<9) /* synonym */
#define _PAGE_DIRTY (1<<10) /* The MIPS dirty bit */
#define _PAGE_SILENT_WRITE (1<<10)
Whereas this on R4k is
#define _PAGE_VALID (1<<7)
#define _PAGE_SILENT_READ (1<<7) /* synonym */
#define _PAGE_DIRTY (1<<8) /* The MIPS dirty bit */
#define _PAGE_SILENT_WRITE (1<<8)
OTOH when following the code paths the pte gets completely replaced
with the swap entry and not bitmasked/and/ored with the original
pte or the ptes flags. So i find no dependencie to the SWP_ macros.
Swapin is in mm/memory.c:do_swap_page
1039 pte = mk_pte(page, vma->vm_page_prot);
1040
1041 /*
1042 * Freeze the "shared"ness of the page, ie page_count + swap_count.
1043 * Must lock page before transferring our swap count to already
1044 * obtained page count.
1045 */
1046 lock_page(page);
1047 swap_free(entry);
1048 if (write_access && !is_page_shared(page))
1049 pte = pte_mkwrite(pte_mkdirty(pte));
1050 UnlockPage(page);
1051
1052 set_pte(page_table, pte);
1053
1054 /* No need to invalidate - it was non-present before */
1055 update_mmu_cache(vma, address, pte);
1056 return 1; /* Minor fault */
The swapout code is in mm/vmscan.c:try_to_swap_out
144 entry = get_swap_page();
145 if (!entry.val)
146 goto out_unlock_restore; /* No swap space left */
147
148 /* Add it to the swap cache and mark it dirty */
149 add_to_swap_cache(page, entry);
150 set_page_dirty(page);
151 goto set_swap_pte;
98 set_swap_pte:
99 swap_duplicate(entry);
100 set_pte(page_table, swp_entry_to_pte(entry));
101 drop_pte:
102 UnlockPage(page);
103 mm->rss--;
104 deactivate_page(page);
105 page_cache_release(page);
106 out_failed:
107 return 0;
108 }
When adding debug code there i can see the flags getting restored
correctly on swapping in.
Flo
--
Florian Lohoff flo@rfc822.org +49-5201-669912
Why is it called "common sense" when nobody seems to have any?
