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locktorture: Add infrastructure for torturing read locks

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Most of it is based on what we already have for writers. This allows
readers to be very independent (and thus configurable), enabling
future module parameters to control things such as rw distribution.
Furthermore, readers have their own delaying function, allowing us
to test different rw critical region latencies, and stress locking
internals. Similarly, statistics, for now will only serve for the
number of lock acquisitions -- as opposed to writers, readers have
no failure detection.

In addition, introduce a new nreaders_stress module parameter. The
default number of readers will be the same number of writers threads.
Writer threads are interleaved with readers. Documentation is updated,
respectively.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Davidlohr Bueso
2014-09-11 21:40:41 -07:00
committed by Paul E. McKenney
parent d36a7a0d5e
commit 4f6332c1dc
2 changed files with 168 additions and 24 deletions
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16
Documentation/locking/locktorture.txt
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@ -29,6 +29,11 @@ nwriters_stress Number of kernel threads that will stress exclusive lock
ownership (writers). The default value is twice the number
of online CPUs.
nreaders_stress Number of kernel threads that will stress shared lock
ownership (readers). The default is the same amount of writer
locks. If the user did not specify nwriters_stress, then
both readers and writers be the amount of online CPUs.
torture_type Type of lock to torture. By default, only spinlocks will
be tortured. This module can torture the following locks,
with string values as follows:
@ -97,15 +102,18 @@ STATISTICS
Statistics are printed in the following format:
spin_lock-torture: Writes: Total: 93746064 Max/Min: 0/0 Fail: 0
(A) (B) (C) (D)
(A) (B) (C) (D) (E)
(A): Lock type that is being tortured -- torture_type parameter.
(B): Number of times the lock was acquired.
(B): Number of writer lock acquisitions. If dealing with a read/write primitive
a second "Reads" statistics line is printed.
(C): Min and max number of times threads failed to acquire the lock.
(C): Number of times the lock was acquired.
(D): true/false values if there were errors acquiring the lock. This should
(D): Min and max number of times threads failed to acquire the lock.
(E): true/false values if there were errors acquiring the lock. This should
-only- be positive if there is a bug in the locking primitive's
implementation. Otherwise a lock should never fail (i.e., spin_lock()).
Of course, the same applies for (C), above. A dummy example of this is