Hi Sage, We're starting a round of work on improving encode/decode workload profiling, which we'll share as soon as we have something informative. Matt ----- "Sage Weil" <sage@xxxxxxxxxxx> wrote: > We talked a bit about improving the performance encode/decode > yesterday at CDS: > > http://pad.ceph.com/p/hammer-buffer_encoding > > I think the main takeaways were: > > 1- We need some up to date profiling information to see > > - how much of it is buffer-related functions (e.g., append) > - which data types are slowest or most frequently encoded (or > otherwise > show up in the profile) > > 2- For now we should probably focus on the efficiency of the > encode/decode > paths. Possibilities include > > - making more things inline > - improving the past path > > 3- Matt and the linuxbox folks have been playing with some general > optimizations for the buffer::list class. These include combining > some of the function of ptr and raw so that, for the common > single-reference case, we chain the raw pointers together directly > from > list using the boost intrusive list type, and fall back to the current > > list -> ptr -> raw strategy when there are additional refs. > > > For #2, one simple thought would be to cache a pointer and remaining > bytes > or end pointer into the append_buffer directly in list so that we > avoid > the duplicate asserts and size checks in the common append (encode) > path. > Then a > > ::encode(myu64, bl); > > would inline into something pretty quick, like > > remaining -= 8; > if (remainining < 0) { // take slow path > > } else { > *ptr = myu64; > ptr += 8; > } > > Not sure if an end pointer would let us cut out the 2 arithmetic ops > or > not. Or if it even matters on modern pipelining processors. > > Anyway, any gains we make here will pay dividends across the entire > code base. And any profiling people want to do will help guide > things... > > Thanks! > sage > -- > 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 -- Matt Benjamin The Linux Box 206 South Fifth Ave. Suite 150 Ann Arbor, MI 48104 http://linuxbox.com tel. 734-761-4689 fax. 734-769-8938 cel. 734-216-5309 -- 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
