Hi Mark, On Jan 17 22:47, Mark Geisert wrote: > Hi Corinna, > Happy New Year back at you! I'm very glad to see you posting again!
Yeah, I took a longer timeout over the holiday season. > Corinna Vinschen via Cygwin-patches wrote: > > Hi Mark, > > > > Happy New Year! > > > > On Dec 21 20:53, Mark Geisert wrote: > > > Replaces function-level lock with data-level lock provided by existing > > > dlmalloc. Sets up to enable dlmalloc's MSPACES, but does not yet enable > > > them due to visible but uninvestigated issues. > > > > > > Single-thread applications may or may not see a performance gain, > > > depending on how heavily it uses the malloc functions. Multi-thread > > > apps will likely see a performance gain. > [...] > > > diff --git a/winsup/cygwin/cygmalloc.h b/winsup/cygwin/cygmalloc.h > > > index 84bad824c..67a9f3b3f 100644 > > > --- a/winsup/cygwin/cygmalloc.h > > > +++ b/winsup/cygwin/cygmalloc.h > [...] > > > +/* These defines tune the dlmalloc implementation in malloc.cc */ > > > # define MALLOC_FAILURE_ACTION __set_ENOMEM () > > > # define USE_DL_PREFIX 1 > > > +# define USE_LOCKS 1 > > > > Just enabling USE_LOCKS looks wrong to me. Before enabling USE_LOCKS, > > you should check how the actual locking is performed. For non WIN32, > > that will be pthread_mutex_lock/unlock, which may not be feasible, > > because it may break expectations during fork. > > I did investigate this before setting it, and I've been running with > '#define USE_LOCKS 1' for many weeks and haven't seen any memory issues of > any kind. Malloc multi-thread stress testing, fork() stress testing, Cygwin > DLL builds, Python and binutils builds, routine X usage; all OK. (Once I > straightened out sped-up mkimport to actually do what Jon T suggested, > blush.) > > > What you may want to do is setting USE_LOCKS to 2, and defining your own > > MLOCK_T/ACQUIRE_LOCK/... macros (in the `#if USE_LOCKS > 1' branch of > > the malloc source, see lines 1798ff), using a type which is non-critical > > during forking, as well as during process initialization. Win32 fast > > R/W Locks come to mind and adding them should be pretty straight-forward. > > This may also allow MSPACES to work OOTB. > > With '#define USE_LOCKS 1' the tangled mess of #if-logic in malloc.cc > resolves on Cygwin to using pthread_mutex_locks, so that seems to be OK > as-is unless what you're suggesting is preferable for speed (or MSPACES when > I get to that). Admittedly, I'm not sure if pthread mutexes pose a problem here, I'm just cautious. Malloc locking is single-process only and pthread mutexes are adding some unnecessary overhead (Event object, bookkeeping list, fixup_after_fork handling). Win32 SRW Locks, especially the exclusive type, is much faster and also easy to use, unless you need recursive locking. Thanks, Corinna
