Revision d7831a0bdf06b9f722b947bb0c205ff7d77cebd8 authored by Richard Kennedy on 30 June 2009, 18:41:35 UTC, committed by Linus Torvalds on 01 July 2009, 01:56:01 UTC
balance_dirty_pages can overreact and move all of the dirty pages to writeback unnecessarily. balance_dirty_pages makes its decision to throttle based on the number of dirty plus writeback pages that are over the calculated limit,so it will continue to move pages even when there are plenty of pages in writeback and less than the threshold still dirty. This allows it to overshoot its limits and move all the dirty pages to writeback while waiting for the drives to catch up and empty the writeback list. A simple fio test easily demonstrates this problem. fio --name=f1 --directory=/disk1 --size=2G -rw=write --name=f2 --directory=/disk2 --size=1G --rw=write --startdelay=10 This is the simplest fix I could find, but I'm not entirely sure that it alone will be enough for all cases. But it certainly is an improvement on my desktop machine writing to 2 disks. Do we need something more for machines with large arrays where bdi_threshold * number_of_drives is greater than the dirty_ratio ? Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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hppb.c
/*
** hppb.c:
** HP-PB bus driver for the NOVA and K-Class systems.
**
** (c) Copyright 2002 Ryan Bradetich
** (c) Copyright 2002 Hewlett-Packard Company
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
*/
#include <linux/types.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/dma-mapping.h>
#include <linux/ioport.h>
#include <asm/io.h>
#include <asm/hardware.h>
#include <asm/parisc-device.h>
struct hppb_card {
unsigned long hpa;
struct resource mmio_region;
struct hppb_card *next;
};
static struct hppb_card hppb_card_head = {
.hpa = 0,
.next = NULL,
};
#define IO_IO_LOW offsetof(struct bc_module, io_io_low)
#define IO_IO_HIGH offsetof(struct bc_module, io_io_high)
/**
* hppb_probe - Determine if the hppb driver should claim this device.
* @dev: The device which has been found
*
* Determine if hppb driver should claim this chip (return 0) or not
* (return 1). If so, initialize the chip and tell other partners in crime
* they have work to do.
*/
static int hppb_probe(struct parisc_device *dev)
{
int status;
struct hppb_card *card = &hppb_card_head;
while(card->next) {
card = card->next;
}
if(card->hpa) {
card->next = kzalloc(sizeof(struct hppb_card), GFP_KERNEL);
if(!card->next) {
printk(KERN_ERR "HP-PB: Unable to allocate memory.\n");
return 1;
}
card = card->next;
}
printk(KERN_INFO "Found GeckoBoa at 0x%x\n", dev->hpa.start);
card->hpa = dev->hpa.start;
card->mmio_region.name = "HP-PB Bus";
card->mmio_region.flags = IORESOURCE_MEM;
card->mmio_region.start = gsc_readl(dev->hpa.start + IO_IO_LOW);
card->mmio_region.end = gsc_readl(dev->hpa.start + IO_IO_HIGH) - 1;
status = ccio_request_resource(dev, &card->mmio_region);
if(status < 0) {
printk(KERN_ERR "%s: failed to claim HP-PB bus space (%08x, %08x)\n",
__FILE__, card->mmio_region.start, card->mmio_region.end);
}
return 0;
}
static struct parisc_device_id hppb_tbl[] = {
{ HPHW_BCPORT, HVERSION_REV_ANY_ID, 0x500, 0xc }, /* E25 and K */
{ HPHW_BCPORT, 0x0, 0x501, 0xc }, /* E35 */
{ HPHW_BCPORT, 0x0, 0x502, 0xc }, /* E45 */
{ HPHW_BCPORT, 0x0, 0x503, 0xc }, /* E55 */
{ 0, }
};
static struct parisc_driver hppb_driver = {
.name = "gecko_boa",
.id_table = hppb_tbl,
.probe = hppb_probe,
};
/**
* hppb_init - HP-PB bus initialization procedure.
*
* Register this driver.
*/
void __init hppb_init(void)
{
register_parisc_driver(&hppb_driver);
}
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