* Re: how is malloc/free done in SMP linux [not found] <199908101513.IAA13569@netcom17.netcom.com> @ 1999-08-11 10:56 ` H.J. Lu 1999-08-11 14:58 ` Wolfram Gloger 0 siblings, 1 reply; 2+ messages in thread From: H.J. Lu @ 1999-08-11 10:56 UTC (permalink / raw) To: Shane Miller; +Cc: GNU C Library > > Sir; > > i am beginning development of a CAD like program. it will be > threaded and multi-processor capable (well thanks to SMP O/S > like linux). > > as to the linux's memory management, suppose a program has > 30 threads. each thread is allocating and deallocating memory. > > does linux block the other 29 threads when thread <X> wants > to malloc/free? how about other threads/processes in the process > table? > > in a regular, single-processor system, my original C++ program > spent 50% of its time in malloc/free. i reduced this time very > significantly by implementing memory pools. the basic algorithm is fairly > easy to split up across threads. hence linux SMP for more performance. > but i am wondering if i might be walking into a "technical snare" > with respect to linux and memory management. > This has little to do with kernel. I forwarded this to the glibc mailing list. -- H.J. Lu (hjl@gnu.org) ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: how is malloc/free done in SMP linux 1999-08-11 10:56 ` how is malloc/free done in SMP linux H.J. Lu @ 1999-08-11 14:58 ` Wolfram Gloger 0 siblings, 0 replies; 2+ messages in thread From: Wolfram Gloger @ 1999-08-11 14:58 UTC (permalink / raw) To: shanem, libc-hacker > > as to the linux's memory management, suppose a program has > > 30 threads. each thread is allocating and deallocating memory. > > > > does linux block the other 29 threads when thread <X> wants > > to malloc/free? Usually, no. Only when two (or more) threads want to simultaneously free() chunks from _one_ particular arena, all those threads except for one will be blocked. In practice, this is very rare. malloc() will actually _never_ block unless more memory is needed from the kernel and the sbrk() or mmap() system call blocks. > how about other threads/processes in the process > > table? Not quite sure, but generally I would expect them to be unaffected by a malloc() or free() in a particular process, unless there is (heavy) swapping activity going on. > > in a regular, single-processor system, my original C++ program > > spent 50% of its time in malloc/free. i reduced this time very > > significantly by implementing memory pools. the basic algorithm is fairly > > easy to split up across threads. hence linux SMP for more performance. > > but i am wondering if i might be walking into a "technical snare" > > with respect to linux and memory management. Linux's malloc may perform well enough so you don't need to implement pools yourself for SMP. Regards, Wolfram. -- `Surf the sea, not double-u three...' wmglo@dent.med.uni-muenchen.de ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~1999-08-11 14:58 UTC | newest] Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <199908101513.IAA13569@netcom17.netcom.com> 1999-08-11 10:56 ` how is malloc/free done in SMP linux H.J. Lu 1999-08-11 14:58 ` Wolfram Gloger
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