From 300b419486c1ca88e33938f182d5d5a8b90fb73f Mon Sep 17 00:00:00 2001 From: Rickard Green Date: Thu, 17 Jun 2010 10:23:50 +0200 Subject: Rewrite ethread library Large parts of the ethread library have been rewritten. The ethread library is an Erlang runtime system internal, portable thread library used by the runtime system itself. Most notable improvement is a reader optimized rwlock implementation which dramatically improve the performance of read-lock/read-unlock operations on multi processor systems by avoiding ping-ponging of the rwlock cache lines. The reader optimized rwlock implementation is used by miscellaneous rwlocks in the runtime system that are known to be read-locked frequently, and can be enabled on ETS tables by passing the `{read_concurrency, true}' option upon table creation. See the documentation of `ets:new/2' for more information. The ethread library can now also use the libatomic_ops library for atomic memory accesses. This makes it possible for the Erlang runtime system to utilize optimized atomic operations on more platforms than before. Use the `--with-libatomic_ops=PATH' configure command line argument when specifying where the libatomic_ops installation is located. The libatomic_ops library can be downloaded from: http://www.hpl.hp.com/research/linux/atomic_ops/ The changed API of the ethread library has also caused modifications in the Erlang runtime system. Preparations for the to come "delayed deallocation" feature has also been done since it depends on the ethread library. Note: When building for x86, the ethread library will now use instructions that first appeared on the pentium 4 processor. If you want the runtime system to be compatible with older processors (back to 486) you need to pass the `--enable-ethread-pre-pentium4-compatibility' configure command line argument when configuring the system. --- erts/doc/src/erl.xml | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'erts/doc/src/erl.xml') diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml index df80142ce1..0e26d62548 100644 --- a/erts/doc/src/erl.xml +++ b/erts/doc/src/erl.xml @@ -603,6 +603,24 @@

Force ets memory block to be moved on realloc.

 + + +

Limits the amount of reader groups used by read/write locks + optimized for read operations in the Erlang runtime system. By + default the reader groups limit equals 8.

+

When the amount of schedulers is less than or equal to the reader + groups limit, each scheduler has its own reader group. When the + amount of schedulers is larger than the reader groups limit, + schedulers share reader groups. Shared reader groups degrades + read lock and read unlock performance while a large amount of + reader groups degrades write lock performance, so the limit is a + tradeoff between performance for read operations and performance + for write operations. Each reader group currently consumes 64 byte + in each read/write lock. Also note that a runtime system using + shared reader groups benefits from binding + schedulers to logical processors, since the reader groups + are distributed better between schedulers.

+

Sets the amount of scheduler threads to create and scheduler -- cgit v1.2.3