On Thu, Mar 07, 2013 at 01:45:33AM -0700, Peter Zijlstra wrote: > On Tue, 2013-03-05 at 15:53 -0500, Rik van Riel wrote: > > > Indeed. Though how well my patches will work with Oracle will > > depend a lot on what kind of semctl syscalls they are doing. > > > > Does Oracle typically do one semop per semctl syscall, or does > > it pass in a whole bunch at once? > > https://oss.oracle.com/~mason/sembench.c > > I think Chris wrote that to match a particular pattern of semaphore > operations the database engine in question does. I haven't checked to > see if it triggers the case in point though. > > Also, Chris since left Oracle but maybe he knows who to poke. >
Dave Kleikamp (cc'd) took over my patches and did the most recent benchmarking. Ported against 3.0: https://oss.oracle.com/git/?p=linux-uek-2.6.39.git;a=commit;h=c7fa322dd72b08450a440ef800124705a1fa148c The current versions are still in the 2.6.32 oracle kernel, but it looks like they reverted this 3.0 commit. I think with Manfred's upstream work my more complex approach wasn't required anymore, but hopefully Dave can fill in details. Here is some of the original discussion around the patch: https://lkml.org/lkml/2010/4/12/257 In terms of how oracle uses IPC, the part that shows up in profiles is using semtimedop for bulk wakeups. They can configure things to use either a bunch of small arrays or a huge single array (and anything in between). There is one IPC semaphore per process and they use this to wait for some event (like a log commit). When the event comes in, everyone waiting is woken in bulk via a semtimedop call. So, single proc waking many waiters at once. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
