At 10:47 AM 6/8/2002 -0700, Brian Pane wrote: >Andi Gutmans wrote: > >>I just checked and it seems like Apache APR memory pools use mutex locking. >>It'd be better to use functions like the Win32 ones which don't use mutex >>locking (as we made sure that only one thread allocates from its pool). >>This could be achieved by compiling apr_pools.c without APR_HAS_THREADS >>but I bet the default Apache 2 build has this enabled. >>Any ideas? >>Andi > > >It's not as bad as it looks. :-) > >The APR pools do locking only in a few situations: > * Creating a new pool > * Creating a subpool of a pool > * Destroying a pool > * Adding space to an existing pool, if it's used up its initial 8KB > allocation > >So the simplest case, the lifetime of a pool looks like: > - create the pool, requiring a lock/unlock > - do hundreds of allocations from the pool, none of which require locking
You mean that different threads can allocate/free memory without requiring locking? How does it accomplish this? > - destroy the pool at the end of the request, requiring one lock/unlock for > the entire thing > >In general, that model works well: over the lifetime of a pool that >handles O(n) allocation operations, we only have to do O(1) lock/unlock >operations. > >But there's an additional optimization that's possible: Sander Striker >added support for thread-specific allocators a while back. The per-request >pools in most of the Apache 2.0 MPMs take advantage of this. Each pool >has an "apr_allocator" object that supplies it with raw memory blocks. >These allocators can be designated as either thread-private or shared >across threads. And a thread-private allocator gets to skip the mutex >operations. The thread-private pool is exactly what we need. That's what we're doing in IIS and it improved performance significantly. Do I have access to these pools by default? What would be the equivalent of the MS HeapCreate(HEAP_NO_SERIALIZE, ..) call? If you're interested take a look at zend_alloc.c and look for Heap. You'll see all of the relevant places. If you could work with me on this it would definitely be good for PHP. We'd just have to find a way to make it work nicely with the SAPI abstraction. It's no problem #ifdef'ing for WIN32 in zend_alloc.c but we can't do the same for SAPI modules. Andi >If you want to try the APR pools, the easiest approach might be to either >use the request_rec->pool directly or create a sub-pool from it. -- PHP Development Mailing List <http://www.php.net/> To unsubscribe, visit: http://www.php.net/unsub.php
