mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-30 23:53:32 +01:00
27 lines
1.2 KiB
Markdown
27 lines
1.2 KiB
Markdown
|
|
||
|
|
## Threads in Tor ##
|
||
|
|
|
||
|
|
Tor is based around a single main thread and one or more worker
|
||
|
|
threads. We aim (with middling success) to use worker threads for
|
||
|
|
CPU-intensive activities and the main thread for our networking.
|
||
|
|
Fortunately (?) we have enough cryptography that moving what we can of the
|
||
|
|
cryptographic processes to the workers should achieve good parallelism under most
|
||
|
|
loads. Unfortunately, we only have a small fraction of our
|
||
|
|
cryptography done in our worker threads right now.
|
||
|
|
|
||
|
|
Our threads-and-workers abstraction is defined in workqueue.c, which
|
||
|
|
combines a work queue with a thread pool, and integrates the
|
||
|
|
signalling with libevent. Tor main instance of a work queue is
|
||
|
|
instantiated in cpuworker.c. It will probably need some refactoring
|
||
|
|
as more types of work are added.
|
||
|
|
|
||
|
|
On a lower level, we provide locks with tor_mutex_t, conditions with
|
||
|
|
tor_cond_t, and thread-local storage with tor_threadlocal_t, all of
|
||
|
|
which are specified in compat_threads.h and implemented in an OS-
|
||
|
|
specific compat_\*threads.h module.
|
||
|
|
|
||
|
|
Try to minimize sharing between threads: it is usually best to simply
|
||
|
|
make the worker "own" all the data it needs while the work is in
|
||
|
|
progress, and to give up ownership when it's complete.
|
||
|
|
|