On Tue, Sep 9, 2014 at 10:50 AM, Sage Weil <sweil@xxxxxxxxxx> wrote: > On Tue, 9 Sep 2014, Andreas Joachim Peters wrote: >> Hi, >> by chance I had a look to the RWLock class. To my best knowledge the way >> you create RW locks it defaults to writer-starvation e.g. all readers >> will always jump a head of a pending writer. I cannot imagine that you >> never have the opposite requirement in the CEPH multithreaded code but I >> didn't review where it is used. In case you are aware, you can just >> ignore this comment, otherwise one could add the option to create a >> writer-prefering RWLock at construction time using e.g. >> pthread_rwlockattr_setkind_np(&attr, PTHREAD_RWLOCK_PREFER_WRITER_NP) > > Hmm, I was not aware. Perhaps we should make the reader vs writer > preference explicit during construction? Yeah, this is interesting as I thought I'd learned somewhere that the default behavior was to prefer writers. Poking around the internet makes me wonder if we actually want to make any changes — best I can tell PTHREAD_RWLOCK_PREFER_WRITER_NP does not actually behave the way one wants (as part of the spec!) because pthreads requires recursive locking, so we'd have to use PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP. But we'd probably want to profile the performance changes (and, uh, run tests to make sure we don't deadlock somehow) before putting any such code upstream. >> Another question: I couldn't find a base implementation to translate >> IPV4/6 ip's to host names? Is there same configuration table/method >> allowing to get back from an OSD address retrieved via >> OSDMap::get_addr() the original host name avoiding the use of DNS >> lookups? > > I don't think we are doing reverse DNS lookups anywhere in the ceph > code ... In particular I think we've looked at doing this before and been unable to reliably map to the *proper* hostname in cases where servers have multiple NICs. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
