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authorRafael J. Wysocki <rjw@sisk.pl>2011-05-15 11:38:48 +0200
committerRafael J. Wysocki <rjw@sisk.pl>2011-05-17 23:19:19 +0200
commitddeb648708108091a641adad0a438ec4fd8bf190 (patch)
tree722367ce903d362af29898db7c2bc2c1058d80c5 /Documentation/ABI
parent13e381365614855bf14c8ad68f9b65e3afd3dd2c (diff)
PM / Hibernate: Add sysfs knob to control size of memory for drivers
Martin reports that on his system hibernation occasionally fails due to the lack of memory, because the radeon driver apparently allocates too much of it during the device freeze stage. It turns out that the amount of memory allocated by radeon during hibernation (and presumably during system suspend too) depends on the utilization of the GPU (e.g. hibernating while there are two KDE 4 sessions with compositing enabled causes radeon to allocate more memory than for one KDE 4 session). In principle it should be possible to use image_size to make the memory preallocation mechanism free enough memory for the radeon driver, but in practice it is not easy to guess the right value because of the way the preallocation code uses image_size. For this reason, it seems reasonable to allow users to control the amount of memory reserved for driver allocations made after the hibernate preallocation, which currently is constant and amounts to 1 MB. Introduce a new sysfs file, /sys/power/reserved_size, whose value will be used as the amount of memory to reserve for the post-preallocation reservations made by device drivers, in bytes. For backwards compatibility, set its default (and initial) value to the currently used number (1 MB). References: https://bugzilla.kernel.org/show_bug.cgi?id=34102 Reported-and-tested-by: Martin Steigerwald <Martin@Lichtvoll.de> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-power14
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 194ca446ac28..b464d12761ba 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -158,3 +158,17 @@ Description:
successful, will make the kernel abort a subsequent transition
to a sleep state if any wakeup events are reported after the
write has returned.
+
+What: /sys/power/reserved_size
+Date: May 2011
+Contact: Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+ The /sys/power/reserved_size file allows user space to control
+ the amount of memory reserved for allocations made by device
+ drivers during the "device freeze" stage of hibernation. It can
+ be written a string representing a non-negative integer that
+ will be used as the amount of memory to reserve for allocations
+ made by device drivers' "freeze" callbacks, in bytes.
+
+ Reading from this file will display the current value, which is
+ set to 1 MB by default.