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>
1 parent df279ca
Raw File
devres.c
#include <linux/pci.h>
#include <linux/io.h>
#include <linux/module.h>

void devm_ioremap_release(struct device *dev, void *res)
{
	iounmap(*(void __iomem **)res);
}

static int devm_ioremap_match(struct device *dev, void *res, void *match_data)
{
	return *(void **)res == match_data;
}

/**
 * devm_ioremap - Managed ioremap()
 * @dev: Generic device to remap IO address for
 * @offset: BUS offset to map
 * @size: Size of map
 *
 * Managed ioremap().  Map is automatically unmapped on driver detach.
 */
void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
			   unsigned long size)
{
	void __iomem **ptr, *addr;

	ptr = devres_alloc(devm_ioremap_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return NULL;

	addr = ioremap(offset, size);
	if (addr) {
		*ptr = addr;
		devres_add(dev, ptr);
	} else
		devres_free(ptr);

	return addr;
}
EXPORT_SYMBOL(devm_ioremap);

/**
 * devm_ioremap_nocache - Managed ioremap_nocache()
 * @dev: Generic device to remap IO address for
 * @offset: BUS offset to map
 * @size: Size of map
 *
 * Managed ioremap_nocache().  Map is automatically unmapped on driver
 * detach.
 */
void __iomem *devm_ioremap_nocache(struct device *dev, resource_size_t offset,
				   unsigned long size)
{
	void __iomem **ptr, *addr;

	ptr = devres_alloc(devm_ioremap_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return NULL;

	addr = ioremap_nocache(offset, size);
	if (addr) {
		*ptr = addr;
		devres_add(dev, ptr);
	} else
		devres_free(ptr);

	return addr;
}
EXPORT_SYMBOL(devm_ioremap_nocache);

/**
 * devm_iounmap - Managed iounmap()
 * @dev: Generic device to unmap for
 * @addr: Address to unmap
 *
 * Managed iounmap().  @addr must have been mapped using devm_ioremap*().
 */
void devm_iounmap(struct device *dev, void __iomem *addr)
{
	iounmap(addr);
	WARN_ON(devres_destroy(dev, devm_ioremap_release, devm_ioremap_match,
			       (void *)addr));
}
EXPORT_SYMBOL(devm_iounmap);

#ifdef CONFIG_HAS_IOPORT
/*
 * Generic iomap devres
 */
static void devm_ioport_map_release(struct device *dev, void *res)
{
	ioport_unmap(*(void __iomem **)res);
}

static int devm_ioport_map_match(struct device *dev, void *res,
				 void *match_data)
{
	return *(void **)res == match_data;
}

/**
 * devm_ioport_map - Managed ioport_map()
 * @dev: Generic device to map ioport for
 * @port: Port to map
 * @nr: Number of ports to map
 *
 * Managed ioport_map().  Map is automatically unmapped on driver
 * detach.
 */
void __iomem * devm_ioport_map(struct device *dev, unsigned long port,
			       unsigned int nr)
{
	void __iomem **ptr, *addr;

	ptr = devres_alloc(devm_ioport_map_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return NULL;

	addr = ioport_map(port, nr);
	if (addr) {
		*ptr = addr;
		devres_add(dev, ptr);
	} else
		devres_free(ptr);

	return addr;
}
EXPORT_SYMBOL(devm_ioport_map);

/**
 * devm_ioport_unmap - Managed ioport_unmap()
 * @dev: Generic device to unmap for
 * @addr: Address to unmap
 *
 * Managed ioport_unmap().  @addr must have been mapped using
 * devm_ioport_map().
 */
void devm_ioport_unmap(struct device *dev, void __iomem *addr)
{
	ioport_unmap(addr);
	WARN_ON(devres_destroy(dev, devm_ioport_map_release,
			       devm_ioport_map_match, (void *)addr));
}
EXPORT_SYMBOL(devm_ioport_unmap);

#ifdef CONFIG_PCI
/*
 * PCI iomap devres
 */
#define PCIM_IOMAP_MAX	PCI_ROM_RESOURCE

struct pcim_iomap_devres {
	void __iomem *table[PCIM_IOMAP_MAX];
};

static void pcim_iomap_release(struct device *gendev, void *res)
{
	struct pci_dev *dev = container_of(gendev, struct pci_dev, dev);
	struct pcim_iomap_devres *this = res;
	int i;

	for (i = 0; i < PCIM_IOMAP_MAX; i++)
		if (this->table[i])
			pci_iounmap(dev, this->table[i]);
}

/**
 * pcim_iomap_table - access iomap allocation table
 * @pdev: PCI device to access iomap table for
 *
 * Access iomap allocation table for @dev.  If iomap table doesn't
 * exist and @pdev is managed, it will be allocated.  All iomaps
 * recorded in the iomap table are automatically unmapped on driver
 * detach.
 *
 * This function might sleep when the table is first allocated but can
 * be safely called without context and guaranteed to succed once
 * allocated.
 */
void __iomem * const * pcim_iomap_table(struct pci_dev *pdev)
{
	struct pcim_iomap_devres *dr, *new_dr;

	dr = devres_find(&pdev->dev, pcim_iomap_release, NULL, NULL);
	if (dr)
		return dr->table;

	new_dr = devres_alloc(pcim_iomap_release, sizeof(*new_dr), GFP_KERNEL);
	if (!new_dr)
		return NULL;
	dr = devres_get(&pdev->dev, new_dr, NULL, NULL);
	return dr->table;
}
EXPORT_SYMBOL(pcim_iomap_table);

/**
 * pcim_iomap - Managed pcim_iomap()
 * @pdev: PCI device to iomap for
 * @bar: BAR to iomap
 * @maxlen: Maximum length of iomap
 *
 * Managed pci_iomap().  Map is automatically unmapped on driver
 * detach.
 */
void __iomem * pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen)
{
	void __iomem **tbl;

	BUG_ON(bar >= PCIM_IOMAP_MAX);

	tbl = (void __iomem **)pcim_iomap_table(pdev);
	if (!tbl || tbl[bar])	/* duplicate mappings not allowed */
		return NULL;

	tbl[bar] = pci_iomap(pdev, bar, maxlen);
	return tbl[bar];
}
EXPORT_SYMBOL(pcim_iomap);

/**
 * pcim_iounmap - Managed pci_iounmap()
 * @pdev: PCI device to iounmap for
 * @addr: Address to unmap
 *
 * Managed pci_iounmap().  @addr must have been mapped using pcim_iomap().
 */
void pcim_iounmap(struct pci_dev *pdev, void __iomem *addr)
{
	void __iomem **tbl;
	int i;

	pci_iounmap(pdev, addr);

	tbl = (void __iomem **)pcim_iomap_table(pdev);
	BUG_ON(!tbl);

	for (i = 0; i < PCIM_IOMAP_MAX; i++)
		if (tbl[i] == addr) {
			tbl[i] = NULL;
			return;
		}
	WARN_ON(1);
}
EXPORT_SYMBOL(pcim_iounmap);

/**
 * pcim_iomap_regions - Request and iomap PCI BARs
 * @pdev: PCI device to map IO resources for
 * @mask: Mask of BARs to request and iomap
 * @name: Name used when requesting regions
 *
 * Request and iomap regions specified by @mask.
 */
int pcim_iomap_regions(struct pci_dev *pdev, u16 mask, const char *name)
{
	void __iomem * const *iomap;
	int i, rc;

	iomap = pcim_iomap_table(pdev);
	if (!iomap)
		return -ENOMEM;

	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
		unsigned long len;

		if (!(mask & (1 << i)))
			continue;

		rc = -EINVAL;
		len = pci_resource_len(pdev, i);
		if (!len)
			goto err_inval;

		rc = pci_request_region(pdev, i, name);
		if (rc)
			goto err_inval;

		rc = -ENOMEM;
		if (!pcim_iomap(pdev, i, 0))
			goto err_region;
	}

	return 0;

 err_region:
	pci_release_region(pdev, i);
 err_inval:
	while (--i >= 0) {
		if (!(mask & (1 << i)))
			continue;
		pcim_iounmap(pdev, iomap[i]);
		pci_release_region(pdev, i);
	}

	return rc;
}
EXPORT_SYMBOL(pcim_iomap_regions);

/**
 * pcim_iomap_regions_request_all - Request all BARs and iomap specified ones
 * @pdev: PCI device to map IO resources for
 * @mask: Mask of BARs to iomap
 * @name: Name used when requesting regions
 *
 * Request all PCI BARs and iomap regions specified by @mask.
 */
int pcim_iomap_regions_request_all(struct pci_dev *pdev, u16 mask,
				   const char *name)
{
	int request_mask = ((1 << 6) - 1) & ~mask;
	int rc;

	rc = pci_request_selected_regions(pdev, request_mask, name);
	if (rc)
		return rc;

	rc = pcim_iomap_regions(pdev, mask, name);
	if (rc)
		pci_release_selected_regions(pdev, request_mask);
	return rc;
}
EXPORT_SYMBOL(pcim_iomap_regions_request_all);

/**
 * pcim_iounmap_regions - Unmap and release PCI BARs
 * @pdev: PCI device to map IO resources for
 * @mask: Mask of BARs to unmap and release
 *
 * Unamp and release regions specified by @mask.
 */
void pcim_iounmap_regions(struct pci_dev *pdev, u16 mask)
{
	void __iomem * const *iomap;
	int i;

	iomap = pcim_iomap_table(pdev);
	if (!iomap)
		return;

	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
		if (!(mask & (1 << i)))
			continue;

		pcim_iounmap(pdev, iomap[i]);
		pci_release_region(pdev, i);
	}
}
EXPORT_SYMBOL(pcim_iounmap_regions);
#endif
#endif
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