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| -rw-r--r-- | gc/README.solaris2 | 65 |
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diff --git a/gc/README.solaris2 b/gc/README.solaris2 deleted file mode 100644 index e593513..0000000 --- a/gc/README.solaris2 +++ /dev/null @@ -1,65 +0,0 @@ -The collector supports both incremental collection and threads under -Solaris 2. The incremental collector normally retrieves page dirty information -through the appropriate /proc calls. But it can also be configured -(by defining MPROTECT_VDB instead of PROC_VDB in gcconfig.h) to use mprotect -and signals. This may result in shorter pause times, but it is no longer -safe to issue arbitrary system calls that write to the heap. - -Under other UNIX versions, -the collector normally obtains memory through sbrk. There is some reason -to expect that this is not safe if the client program also calls the system -malloc, or especially realloc. The sbrk man page strongly suggests this is -not safe: "Many library routines use malloc() internally, so use brk() -and sbrk() only when you know that malloc() definitely will not be used by -any library routine." This doesn't make a lot of sense to me, since there -seems to be no documentation as to which routines can transitively call malloc. -Nonetheless, under Solaris2, the collector now (since 4.12) allocates -memory using mmap by default. (It defines USE_MMAP in gcconfig.h.) -You may want to reverse this decisions if you use -DREDIRECT_MALLOC=... - - -SOLARIS THREADS: - -The collector must be compiled with -DSOLARIS_THREADS to be thread safe. -It is also essential that gc.h be included in files that call thr_create, -thr_join, thr_suspend, thr_continue, or dlopen. Gc.h macro defines -these to also do GC bookkeeping, etc. Gc.h must be included with -SOLARIS_THREADS defined, otherwise these replacements are not visible. -A collector built in this way way only be used by programs that are -linked with the threads library. - -If you are using the Pthreads interface, also define _SOLARIS_PTHREADS. - -In this mode, the collector contains various workarounds for older Solaris -bugs. Mostly, these should not be noticeable unless you look at system -call traces. However, it cannot protect a guard page at the end of -a thread stack. If you know that you will only be running Solaris2.5 -or later, it should be possible to fix this by compiling the collector -with -DSOLARIS23_MPROTECT_BUG_FIXED. - -Jeremy Fitzhardinge points out that there is a problem with the dlopen -replacement, in that startup code in the library is run while the allocation -lock is held. This appears to be difficult to fix, since the collector does -look at data structures maintained by dlopen, and hence some locking is needed -around the dlopen call. Defining USE_PROC_FOR_LIBRARIES will get address -space layout information from /proc avoiding the dlopen lock. But this has -other disadvanatages, e.g. mmapped files may be scanned. - -If solaris_threads are used on an X86 processor with malloc redirected to -GC_malloc, it is necessary to call GC_thr_init explicitly before forking the -first thread. (This avoids a deadlock arising from calling GC_thr_init -with the allocation lock held.) - -It appears that there is a problem in using gc_cpp.h in conjunction with -Solaris threads and Sun's C++ runtime. Apparently the overloaded new operator -is invoked by some iostream initialization code before threads are correctly -initialized. As a result, call to thr_self() in garbage collector -initialization segfaults. Currently the only known workaround is to not -invoke the garbage collector from a user defined global operator new, or to -have it invoke the garbage-collector's allocators only after main has started. -(Note that the latter requires a moderately expensive test in operator -delete.) - -Hans-J. Boehm -(The above contains my personal opinions, which are probably not shared -by anyone else.) |