Re: [PATCH] improve speed of freeing bootmem

Josh Aas
2004-08-06T22:02:33Z

[-- Attachment #1: Type: text/plain, Size: 1970 bytes --]

New patch is attached.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Josh Aas <josha@sgi.com>

--
Josh Aas
Silicon Graphics, Inc. (SGI)
Linux System Software
651-683-3068

Andrew Morton wrote:
> Josh Aas <josha@sgi.com> wrote:
>
>>Attached is a patch that greatly improves the speed of freeing boot
>>memory.
>
>
> hm, OK. I have a vague feeling that Bill Irwin had patches to fix this up
> ages ago.
>
>
> A few nits:
>
>
>>--- a/mm/bootmem.c 2004-08-05 15:33:39.000000000 -0500
>>+++ b/mm/bootmem.c 2004-08-06 13:42:33.000000000 -0500
>>@@ -259,6 +259,7 @@ static unsigned long __init free_all_boo
>> unsigned long i, count, total = 0;
>> unsigned long idx;
>> unsigned long *map;
>>+ int gofast = 0;
>>
>> BUG_ON(!bdata->node_bootmem_map);
>>
>>@@ -267,14 +268,32 @@ static unsigned long __init free_all_boo
>> page = virt_to_page(phys_to_virt(bdata->node_boot_start));
>> idx = bdata->node_low_pfn - (bdata->node_boot_start >> PAGE_SHIFT);
>> map = bdata->node_bootmem_map;
>>+ if (bdata->node_boot_start == 0 ||
>>+ ffs(bdata->node_boot_start) - PAGE_SHIFT > ffs(BITS_PER_LONG))
>>+ gofast = 1;
>
>
> A comment describing the above reasoning would be nice.
>
>
>> for (i = 0; i < idx; ) {
>> unsigned long v = ~map[i / BITS_PER_LONG];
>>- if (v) {
>>+ if (gofast && v == ~0UL) {
>>+ int j;
>>+
>>+ count += BITS_PER_LONG;
>>+ ClearPageReservedNoAtomic(page);
>>+ set_page_count(page, 1);
>>+ for (j = 1; j < BITS_PER_LONG; j++) {
>>+ if (j + 16 < BITS_PER_LONG) {
>>+ prefetchw(page + j + 16);
>>+ }
>
>
> The whitespace/tabbing has gone funny here.
>
>
>>+#define ClearPageReservedNoAtomic(page) (page)->flags &= ~(1UL << PG_reserved)
>
>
> The naming convention we used in 2.4 for the nonatomic operation was
> __ClearPageReserved(), so can we please stick with that?
>
> And this macro can use __clear_bit() rather than open-coding it.

[-- Attachment #2: bootmem5.patch --]
[-- Type: text/x-patch, Size: 2384 bytes --]

--- mm/bootmem.c.orig 2004-08-05 15:33:39.000000000 -0500
+++ mm/bootmem.c 2004-08-06 16:52:41.000000000 -0500
@@ -259,6 +259,7 @@ static unsigned long __init free_all_boo
unsigned long i, count, total = 0;
unsigned long idx;
unsigned long *map;
+ int gofast = 0;

BUG_ON(!bdata->node_bootmem_map);

@@ -267,14 +268,33 @@ static unsigned long __init free_all_boo
page = virt_to_page(phys_to_virt(bdata->node_boot_start));
idx = bdata->node_low_pfn - (bdata->node_boot_start >> PAGE_SHIFT);
map = bdata->node_bootmem_map;
+ /* Check physaddr is O(LOG2(BITS_PER_LONG)) page aligned */
+ if (bdata->node_boot_start == 0 ||
+ ffs(bdata->node_boot_start) - PAGE_SHIFT > ffs(BITS_PER_LONG))
+ gofast = 1;
for (i = 0; i < idx; ) {
unsigned long v = ~map[i / BITS_PER_LONG];
- if (v) {
+ if (gofast && v == ~0UL) {
+ int j;
+
+ count += BITS_PER_LONG;
+ __ClearPageReserved(page);
+ set_page_count(page, 1);
+ for (j = 1; j < BITS_PER_LONG; j++) {
+ if (j + 16 < BITS_PER_LONG) {
+ prefetchw(page + j + 16);
+ }
+ __ClearPageReserved(page + j);
+ }
+ __free_pages(page, ffs(BITS_PER_LONG)-1);
+ i += BITS_PER_LONG;
+ page += BITS_PER_LONG;
+ } else if (v) {
unsigned long m;
for (m = 1; m && i < idx; m<<=1, page++, i++) {
if (v & m) {
count++;
- ClearPageReserved(page);
+ __ClearPageReserved(page);
set_page_count(page, 1);
__free_page(page);
}
@@ -294,7 +314,7 @@ static unsigned long __init free_all_boo
count = 0;
for (i = 0; i < ((bdata->node_low_pfn-(bdata->node_boot_start >> PAGE_SHIFT))/8 + PAGE_SIZE-1)/PAGE_SIZE; i++,page++) {
count++;
- ClearPageReserved(page);
+ __ClearPageReserved(page);
set_page_count(page, 1);
__free_page(page);
}
--- include/linux/page-flags.h.orig 2004-08-06 13:43:36.000000000 -0500
+++ include/linux/page-flags.h 2004-08-06 15:16:29.000000000 -0500
@@ -236,6 +236,7 @@ extern unsigned long __read_page_state(u
#define PageReserved(page) test_bit(PG_reserved, &(page)->flags)
#define SetPageReserved(page) set_bit(PG_reserved, &(page)->flags)
#define ClearPageReserved(page) clear_bit(PG_reserved, &(page)->flags)
+#define __ClearPageReserved(page) __clear_bit(PG_reserved, &(page)->flags)

#define SetPagePrivate(page) set_bit(PG_private, &(page)->flags)
#define ClearPagePrivate(page) clear_bit(PG_private, &(page)->flags)