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-rw-r--r--Documentation/ABI/testing/sysfs-class-bdi43
1 files changed, 15 insertions, 28 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index c55e811ca180..5ac1e01bbd48 100644
--- a/Documentation/ABI/testing/sysfs-class-bdi
+++ b/Documentation/ABI/testing/sysfs-class-bdi
@@ -3,8 +3,8 @@ Date: January 2008
3Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 3Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
4Description: 4Description:
5 5
6Provide a place in sysfs for the backing_dev_info object. 6Provide a place in sysfs for the backing_dev_info object. This allows
7This allows us to see and set the various BDI specific variables. 7setting and retrieving various BDI specific variables.
8 8
9The <bdi> identifier can be either of the following: 9The <bdi> identifier can be either of the following:
10 10
@@ -26,34 +26,21 @@ read_ahead_kb (read-write)
26 26
27 Size of the read-ahead window in kilobytes 27 Size of the read-ahead window in kilobytes
28 28
29reclaimable_kb (read-only)
30
31 Reclaimable (dirty or unstable) memory destined for writeback
32 to this device
33
34writeback_kb (read-only)
35
36 Memory currently under writeback to this device
37
38dirty_kb (read-only)
39
40 Global threshold for reclaimable + writeback memory
41
42bdi_dirty_kb (read-only)
43
44 Current threshold on this BDI for reclaimable + writeback
45 memory
46
47min_ratio (read-write) 29min_ratio (read-write)
48 30
49 Minimal percentage of global dirty threshold allocated to this 31 Under normal circumstances each device is given a part of the
50 bdi. If the value written to this file would make the the sum 32 total write-back cache that relates to its current average
51 of all min_ratio values exceed 100, then EINVAL is returned. 33 writeout speed in relation to the other devices.
52 If min_ratio would become larger than the current max_ratio, 34
53 then also EINVAL is returned. The default is zero 35 The 'min_ratio' parameter allows assigning a minimum
36 percentage of the write-back cache to a particular device.
37 For example, this is useful for providing a minimum QoS.
54 38
55max_ratio (read-write) 39max_ratio (read-write)
56 40
57 Maximal percentage of global dirty threshold allocated to this 41 Allows limiting a particular device to use not more than the
58 bdi. If max_ratio would become smaller than the current 42 given percentage of the write-back cache. This is useful in
59 min_ratio, then EINVAL is returned. The default is 100 43 situations where we want to avoid one device taking all or
44 most of the write-back cache. For example in case of an NFS
45 mount that is prone to get stuck, or a FUSE mount which cannot
46 be trusted to play fair.