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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mca-device.c
/* -*- mode: c; c-basic-offset: 8 -*- */
/*
* MCA device support functions
*
* These functions support the ongoing device access API.
*
* (C) 2002 James Bottomley <James.Bottomley@HansenPartnership.com>
*
**-----------------------------------------------------------------------------
**
** 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.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
**-----------------------------------------------------------------------------
*/
#include <linux/module.h>
#include <linux/device.h>
#include <linux/mca.h>
#include <linux/string.h>
/**
* mca_device_read_stored_pos - read POS register from stored data
* @mca_dev: device to read from
* @reg: register to read from
*
* Fetch a POS value that was stored at boot time by the kernel
* when it scanned the MCA space. The register value is returned.
* Missing or invalid registers report 0.
*/
unsigned char mca_device_read_stored_pos(struct mca_device *mca_dev, int reg)
{
if(reg < 0 || reg >= 8)
return 0;
return mca_dev->pos[reg];
}
EXPORT_SYMBOL(mca_device_read_stored_pos);
/**
* mca_device_read_pos - read POS register from card
* @mca_dev: device to read from
* @reg: register to read from
*
* Fetch a POS value directly from the hardware to obtain the
* current value. This is much slower than
* mca_device_read_stored_pos and may not be invoked from
* interrupt context. It handles the deep magic required for
* onboard devices transparently.
*/
unsigned char mca_device_read_pos(struct mca_device *mca_dev, int reg)
{
struct mca_bus *mca_bus = to_mca_bus(mca_dev->dev.parent);
return mca_bus->f.mca_read_pos(mca_dev, reg);
return mca_dev->pos[reg];
}
EXPORT_SYMBOL(mca_device_read_pos);
/**
* mca_device_write_pos - read POS register from card
* @mca_dev: device to write pos register to
* @reg: register to write to
* @byte: byte to write to the POS registers
*
* Store a POS value directly to the hardware. You should not
* normally need to use this function and should have a very good
* knowledge of MCA bus before you do so. Doing this wrongly can
* damage the hardware.
*
* This function may not be used from interrupt context.
*
*/
void mca_device_write_pos(struct mca_device *mca_dev, int reg,
unsigned char byte)
{
struct mca_bus *mca_bus = to_mca_bus(mca_dev->dev.parent);
mca_bus->f.mca_write_pos(mca_dev, reg, byte);
}
EXPORT_SYMBOL(mca_device_write_pos);
/**
* mca_device_transform_irq - transform the ADF obtained IRQ
* @mca_device: device whose irq needs transforming
* @irq: input irq from ADF
*
* MCA Adapter Definition Files (ADF) contain irq, ioport, memory
* etc. definitions. In systems with more than one bus, these need
* to be transformed through bus mapping functions to get the real
* system global quantities.
*
* This function transforms the interrupt number and returns the
* transformed system global interrupt
*/
int mca_device_transform_irq(struct mca_device *mca_dev, int irq)
{
struct mca_bus *mca_bus = to_mca_bus(mca_dev->dev.parent);
return mca_bus->f.mca_transform_irq(mca_dev, irq);
}
EXPORT_SYMBOL(mca_device_transform_irq);
/**
* mca_device_transform_ioport - transform the ADF obtained I/O port
* @mca_device: device whose port needs transforming
* @ioport: input I/O port from ADF
*
* MCA Adapter Definition Files (ADF) contain irq, ioport, memory
* etc. definitions. In systems with more than one bus, these need
* to be transformed through bus mapping functions to get the real
* system global quantities.
*
* This function transforms the I/O port number and returns the
* transformed system global port number.
*
* This transformation can be assumed to be linear for port ranges.
*/
int mca_device_transform_ioport(struct mca_device *mca_dev, int port)
{
struct mca_bus *mca_bus = to_mca_bus(mca_dev->dev.parent);
return mca_bus->f.mca_transform_ioport(mca_dev, port);
}
EXPORT_SYMBOL(mca_device_transform_ioport);
/**
* mca_device_transform_memory - transform the ADF obtained memory
* @mca_device: device whose memory region needs transforming
* @mem: memory region start from ADF
*
* MCA Adapter Definition Files (ADF) contain irq, ioport, memory
* etc. definitions. In systems with more than one bus, these need
* to be transformed through bus mapping functions to get the real
* system global quantities.
*
* This function transforms the memory region start and returns the
* transformed system global memory region (physical).
*
* This transformation can be assumed to be linear for region ranges.
*/
void *mca_device_transform_memory(struct mca_device *mca_dev, void *mem)
{
struct mca_bus *mca_bus = to_mca_bus(mca_dev->dev.parent);
return mca_bus->f.mca_transform_memory(mca_dev, mem);
}
EXPORT_SYMBOL(mca_device_transform_memory);
/**
* mca_device_claimed - check if claimed by driver
* @mca_dev: device to check
*
* Returns 1 if the slot has been claimed by a driver
*/
int mca_device_claimed(struct mca_device *mca_dev)
{
return mca_dev->driver_loaded;
}
EXPORT_SYMBOL(mca_device_claimed);
/**
* mca_device_set_claim - set the claim value of the driver
* @mca_dev: device to set value for
* @val: claim value to set (1 claimed, 0 unclaimed)
*/
void mca_device_set_claim(struct mca_device *mca_dev, int val)
{
mca_dev->driver_loaded = val;
}
EXPORT_SYMBOL(mca_device_set_claim);
/**
* mca_device_status - get the status of the device
* @mca_device: device to get
*
* returns an enumeration of the device status:
*
* MCA_ADAPTER_NORMAL adapter is OK.
* MCA_ADAPTER_NONE no adapter at device (should never happen).
* MCA_ADAPTER_DISABLED adapter is disabled.
* MCA_ADAPTER_ERROR adapter cannot be initialised.
*/
enum MCA_AdapterStatus mca_device_status(struct mca_device *mca_dev)
{
return mca_dev->status;
}
EXPORT_SYMBOL(mca_device_status);
/**
* mca_device_set_name - set the name of the device
* @mca_device: device to set the name of
* @name: name to set
*/
void mca_device_set_name(struct mca_device *mca_dev, const char *name)
{
if(!mca_dev)
return;
strlcpy(mca_dev->name, name, sizeof(mca_dev->name));
}
EXPORT_SYMBOL(mca_device_set_name);
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