Re: [PATCH] improve speed of freeing bootmem

Andrew Morton
2004-08-06T19:52:16Z

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.