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Commit d1bbdd66 authored by Mike Ditto's avatar Mike Ditto Committed by Ingo Molnar
Browse files

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: default avatarMike 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9af0c7a6

arch/x86/kernel/e820.c

+24 −35
Original line number Diff line number Diff line
@@ -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_

 */



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 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)

{

	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 */