On 03/07/2013 06:55 AM, Chris Mason wrote: > 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.
>From what I recall, I could never get better performance from your patches that we saw with Manfred's work alone. I can't remember the reasons for including and then reverting the patches from the 3.0 (2.6.39) Oracle kernel, but in the end we weren't able to justify their inclusion. > 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/
