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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README.dino
/*
** HP VISUALIZE Workstation PCI Bus Defect
**
** "HP has discovered a potential system defect that can affect
** the behavior of five models of HP VISUALIZE workstations when
** equipped with third-party or customer-installed PCI I/O expansion
** cards. The defect is limited to the HP C180, C160, C160L, B160L,
** and B132L VISUALIZE workstations, and will only be encountered
** when data is transmitted through PCI I/O expansion cards on the
** PCI bus. HP-supplied graphics cards that utilize the PCI bus are
** not affected."
**
** REVISIT: "go/pci_defect" link below is stale.
** HP Internal can use <http://hpfcdma.fc.hp.com:80/Dino/>
**
** Product First Good Serial Number
** C200/C240 (US) US67350000
**B132L+/B180 (US) US67390000
** C200 (Europe) 3713G01000
** B180L (Europe) 3720G01000
**
** Note that many boards were fixed/replaced under a free replacement
** program. Assume a machine is only "suspect" until proven otherwise.
**
** "The pci_check program will also be available as application
** patch PHSS_12295"
*/
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