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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-13 16:34:22 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-08-20 09:00:14 -0700
commit5cc6517abdeccb6690b344a43b5ce8eaee82da3c (patch)
treeb18000bcdd57bc976a4658106395f86cf553c464 /Documentation/RCU/checklist.txt
parenta3dc3fb161f9b4066c0fce22db72638af8baf83b (diff)
downloadlinux-linaro-stable-5cc6517abdeccb6690b344a43b5ce8eaee82da3c.tar.gz
rcu: document ways of stalling updates in low-memory situations
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'Documentation/RCU/checklist.txt')
-rw-r--r--Documentation/RCU/checklist.txt23
1 files changed, 16 insertions, 7 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index c7c6788956f4..0c134f8afc6f 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -218,13 +218,22 @@ over a rather long period of time, but improvements are always welcome!
include:
a. Keeping a count of the number of data-structure elements
- used by the RCU-protected data structure, including those
- waiting for a grace period to elapse. Enforce a limit
- on this number, stalling updates as needed to allow
- previously deferred frees to complete.
-
- Alternatively, limit only the number awaiting deferred
- free rather than the total number of elements.
+ used by the RCU-protected data structure, including
+ those waiting for a grace period to elapse. Enforce a
+ limit on this number, stalling updates as needed to allow
+ previously deferred frees to complete. Alternatively,
+ limit only the number awaiting deferred free rather than
+ the total number of elements.
+
+ One way to stall the updates is to acquire the update-side
+ mutex. (Don't try this with a spinlock -- other CPUs
+ spinning on the lock could prevent the grace period
+ from ever ending.) Another way to stall the updates
+ is for the updates to use a wrapper function around
+ the memory allocator, so that this wrapper function
+ simulates OOM when there is too much memory awaiting an
+ RCU grace period. There are of course many other
+ variations on this theme.
b. Limiting update rate. For example, if updates occur only
once per hour, then no explicit rate limiting is required,