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arch/x86/kernel/e820.c: Eliminate bubble sort from sanitize_e820_map() 

Replace the bubble sort in sanitize_e820_map() with a call to
the generic kernel sort function to avoid pathological
performance with large maps.

On large (thousands of entries) E820 maps, the previous code
took minutes to run; with this change it's now milliseconds.

Signed-off-by: Mike Ditto <mditto@google.com>
Cc: sassmann@kpanic.de
Cc: yuenn@google.com
Cc: Stefan Assmann <sassmann@kpanic.de>
Cc: Nancy Yuen <yuenn@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Ditto 2011-11-15 14:46:50 -08:00 committed by Ingo Molnar
parent 9af0c7a6fa
commit d1bbdd6692
1 changed files with 24 additions and 35 deletions
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59
arch/x86/kernel/e820.c
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@ -19,6 +19,7 @@
#include <linux/acpi.h>
#include <linux/firmware-map.h>
#include <linux/memblock.h>
#include <linux/sort.h>
#include <asm/e820.h>
#include <asm/proto.h>
@ -227,22 +228,38 @@ void __init e820_print_map(char *who)
* ____________________33__
* ______________________4_
*/
struct change_member {
struct e820entry *pbios; /* pointer to original bios entry */
unsigned long long addr; /* address for this change point */
};
static int __init cpcompare(const void *a, const void *b)
{
struct change_member * const *app = a, * const *bpp = b;
const struct change_member *ap = *app, *bp = *bpp;
/*
* Inputs are pointers to two elements of change_point[]. If their
* addresses are unequal, their difference dominates. If the addresses
* are equal, then consider one that represents the end of its region
* to be greater than one that does not.
*/
if (ap->addr != bp->addr)
return ap->addr > bp->addr ? 1 : -1;
return (ap->addr != ap->pbios->addr) - (bp->addr != bp->pbios->addr);
}
int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
u32 *pnr_map)
{
struct change_member {
struct e820entry *pbios; /* pointer to original bios entry */
unsigned long long addr; /* address for this change point */
};
static struct change_member change_point_list[2*E820_X_MAX] __initdata;
static struct change_member *change_point[2*E820_X_MAX] __initdata;
static struct e820entry *overlap_list[E820_X_MAX] __initdata;
static struct e820entry new_bios[E820_X_MAX] __initdata;
struct change_member *change_tmp;
unsigned long current_type, last_type;
unsigned long long last_addr;
int chgidx, still_changing;
int chgidx;
int overlap_entries;
int new_bios_entry;
int old_nr, new_nr, chg_nr;
@ -279,35 +296,7 @@ int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
chg_nr = chgidx;
/* sort change-point list by memory addresses (low -> high) */
still_changing = 1;
while (still_changing) {
still_changing = 0;
for (i = 1; i < chg_nr; i++) {
unsigned long long curaddr, lastaddr;
unsigned long long curpbaddr, lastpbaddr;
curaddr = change_point[i]->addr;
lastaddr = change_point[i - 1]->addr;
curpbaddr = change_point[i]->pbios->addr;
lastpbaddr = change_point[i - 1]->pbios->addr;
/*
* swap entries, when:
*
* curaddr > lastaddr or
* curaddr == lastaddr and curaddr == curpbaddr and
* lastaddr != lastpbaddr
*/
if (curaddr < lastaddr ||
(curaddr == lastaddr && curaddr == curpbaddr &&
lastaddr != lastpbaddr)) {
change_tmp = change_point[i];
change_point[i] = change_point[i-1];
change_point[i-1] = change_tmp;
still_changing = 1;
}
}
}
sort(change_point, chg_nr, sizeof *change_point, cpcompare, 0);
/* create a new bios memory map, removing overlaps */
overlap_entries = 0; /* number of entries in the overlap table */