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Persistent grants feature provides high scalability. On some small systems, however, it could incur data copy overheads[1] and thus it is required to be disabled. But, there is no option to disable it. For the reason, this commit adds a module parameter for disabling of the feature. [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability Signed-off-by: Anthony Liguori <aliguori@amazon.com> Signed-off-by: SeongJae Park <sjpark@amazon.de> Reviewed-by: Juergen Gross <jgross@suse.com> Acked-by: Roger Pau Monné <roger.pau@citrix.com> Link: https://lore.kernel.org/r/20200923061841.20531-2-sjpark@amazon.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
46 lines
1.9 KiB
Text
46 lines
1.9 KiB
Text
What: /sys/module/xen_blkback/parameters/max_buffer_pages
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Date: March 2013
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KernelVersion: 3.11
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Contact: Roger Pau Monné <roger.pau@citrix.com>
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Description:
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Maximum number of free pages to keep in each block
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backend buffer.
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What: /sys/module/xen_blkback/parameters/max_persistent_grants
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Date: March 2013
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KernelVersion: 3.11
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Contact: Roger Pau Monné <roger.pau@citrix.com>
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Description:
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Maximum number of grants to map persistently in
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blkback. If the frontend tries to use more than
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max_persistent_grants, the LRU kicks in and starts
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removing 5% of max_persistent_grants every 100ms.
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What: /sys/module/xen_blkback/parameters/persistent_grant_unused_seconds
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Date: August 2018
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KernelVersion: 4.19
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Contact: Roger Pau Monné <roger.pau@citrix.com>
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Description:
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How long a persistent grant is allowed to remain
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allocated without being in use. The time is in
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seconds, 0 means indefinitely long.
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The default is 60 seconds.
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What: /sys/module/xen_blkback/parameters/buffer_squeeze_duration_ms
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Date: December 2019
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KernelVersion: 5.6
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Contact: SeongJae Park <sjpark@amazon.de>
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Description:
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When memory pressure is reported to blkback this option
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controls the duration in milliseconds that blkback will not
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cache any page not backed by a grant mapping.
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The default is 10ms.
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What: /sys/module/xen_blkback/parameters/feature_persistent
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Date: September 2020
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KernelVersion: 5.10
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Contact: SeongJae Park <sjpark@amazon.de>
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Description:
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Whether to enable the persistent grants feature or not. Note
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that this option only takes effect on newly created backends.
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The default is Y (enable).
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