Date: Wed, 20 Aug 2003 13:17:13 -0400
From: Jeff Garzik <jgarzik@pobox.com>
To: M?ns Rullg?rd <mru@users.sourceforge.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: how to turn off, or to clear read cache?
Message-ID: <20030820171713.GA21822@gtf.org>
References: <200308201322.h7KDMQga000797@81-2-122-30.bradfords.org.uk> <3F437646.4050107@gamic.com> <yw1x8ypocv63.fsf@users.sourceforge.net> <20030820164949.GA5613@lsd.di.uminho.pt> <yw1xptj0b72s.fsf@users.sourceforge.net>
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On Wed, Aug 20, 2003 at 06:57:15PM +0200, M?ns Rullg?rd wrote:
> Luciano Miguel Ferreira Rocha <luciano@lsd.di.uminho.pt> writes:
> > Will it clear the cache?
> 
> It will probably clear some cache to make room for cache from hda.
> 
> perl -e '@f[0..100000000]=0'
> 
> will do it faster.

Using fillmem will do it better :)

	Jeff


/* fillmem.c usage: "fillmem <number-of-megabytes>" */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

#define MEGS 140	/* default; override on command line */
#define MEG (1024 * 1024)

int main (int argc, char *argv[])
{
	void **data;
	int i, r;
	size_t megs = MEGS;

	if ((argc >= 2) && (atoi(argv[1]) > 0))
		megs = atoi(argv[1]);

	data = malloc (megs * sizeof (void*));
	if (!data) abort();

	memset (data, 0, megs * sizeof (void*));

	srand(time(NULL));

	for (i = 0; i < megs; i++) {
		data[i] = malloc(MEG);
		memset (data[i], i, MEG);
		printf("malloc/memset %03d/%03lu\n", i+1, megs);
	}
	for (i = megs - 1; i >= 0; i--) {
		r = rand() % 200;
		memset (data[i], r, MEG);
		printf("memset #2 %03d/%03lu = %d\n", i+1, megs, r);
	}
	printf("done\n");
	return 0;
}
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