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Diffstat (limited to 'manual/tunables.texi')
| -rw-r--r-- | manual/tunables.texi | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/manual/tunables.texi b/manual/tunables.texi index f503daef56..e851b95c59 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -31,6 +31,7 @@ their own namespace. @menu * Tunable names:: The structure of a tunable name * Memory Allocation Tunables:: Tunables in the memory allocation subsystem +* Elision Tunables:: Tunables in elision subsystem * Hardware Capability Tunables:: Tunables that modify the hardware capabilities seen by @theglibc{} @end menu @@ -212,6 +213,74 @@ pre-fill the per-thread cache with. The default, or when set to zero, is no limit. @end deftp +@node Elision Tunables +@section Elision Tunables +@cindex elision tunables +@cindex tunables, elision + +@deftp {Tunable namespace} glibc.elision +Contended locks are usually slow and can lead to performance and scalability +issues in multithread code. Lock elision will use memory transactions to under +certain conditions, to elide locks and improve performance. +Elision behavior can be modified by setting the following tunables in +the @code{elision} namespace: +@end deftp + +@deftp Tunable glibc.elision.enable +The @code{glibc.elision.enable} tunable enables lock elision if the feature is +supported by the hardware. If elision is not supported by the hardware this +tunable has no effect. + +Elision tunables are supported for 64-bit Intel, IBM POWER, and z System +architectures. +@end deftp + +@deftp Tunable glibc.elision.skip_lock_busy +The @code{glibc.elision.skip_lock_busy} tunable sets how many times to use a +non-transactional lock after a transactional failure has occurred because the +lock is already acquired. Expressed in number of lock acquisition attempts. + +The default value of this tunable is @samp{3}. +@end deftp + +@deftp Tunable glibc.elision.skip_lock_internal_abort +The @code{glibc.elision.skip_lock_internal_abort} tunable sets how many times +the thread should avoid using elision if a transaction aborted for any reason +other than a different thread's memory accesses. Expressed in number of lock +acquisition attempts. + +The default value of this tunable is @samp{3}. +@end deftp + +@deftp Tunable glibc.elision.skip_lock_after_retries +The @code{glibc.elision.skip_lock_after_retries} tunable sets how many times +to try to elide a lock with transactions, that only failed due to a different +thread's memory accesses, before falling back to regular lock. +Expressed in number of lock elision attempts. + +This tunable is supported only on IBM POWER, and z System architectures. + +The default value of this tunable is @samp{3}. +@end deftp + +@deftp Tunable glibc.elision.tries +The @code{glibc.elision.tries} sets how many times to retry elision if there is +chance for the transaction to finish execution e.g., it wasn't +aborted due to the lock being already acquired. If elision is not supported +by the hardware this tunable is set to @samp{0} to avoid retries. + +The default value of this tunable is @samp{3}. +@end deftp + +@deftp Tunable glibc.elision.skip_trylock_internal_abort +The @code{glibc.elision.skip_trylock_internal_abort} tunable sets how many +times the thread should avoid trying the lock if a transaction aborted due to +reasons other than a different thread's memory accesses. Expressed in number +of try lock attempts. + +The default value of this tunable is @samp{3}. +@end deftp + @node Hardware Capability Tunables @section Hardware Capability Tunables @cindex hardware capability tunables |