On Thu, 30 Oct 2014, Haomai Wang wrote:
> I'm interested in bufferlist's own encode/decode performance. But as I
> performed until now, I think we need to consider change caller's
> behavior to get better performance.
>
> Combined
> (https://wiki.ceph.com/Planning/Blueprints/Hammer/Fixed_memory_layout_for_Message%2F%2FOp_passing)
> with
> bp(https://wiki.ceph.com/Planning/Blueprints/Hammer/osd%3A_update_Transaction_encoding),
> I'm going to seeking a way to reduce encode/decodes calls.
>
> Mainly, we have three points:
> 1. Make ObjectStore::Transaction's metadata and data separated
> 2. No copy for op's data from Messenger to ObjectStore
> 3. Avoid encode/decode for ObjectStore::OP instead of fixed-size memory layout
>
> We have a simple perf test results and a overview design ppt. Hope we
> can have a talk at 8:00(CST).
Yep! For reference, the blueprint I wrote is here:
https://wiki.ceph.com/Planning/Blueprints/Hammer/osd%3A_update_Transaction_encoding
but I think we'll want to discuss Haomai's approach as well.
This is at 17:15 PDT, 01:15 CET, 08:15 CST for those that want to join.
https://wiki.ceph.com/Planning/CDS/Hammer_(Oct_2014)
sage
>
> On Thu, Oct 30, 2014 at 1:23 AM, Matt W. Benjamin <[email protected]> wrote:
> > 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" <[email protected]> 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
> >> --
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> >> in
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> >
> > --
> > Matt Benjamin
> > The Linux Box
> > 206 South Fifth Ave. Suite 150
> > Ann Arbor, MI 48104
> >
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> >
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> > fax. 734-769-8938
> > cel. 734-216-5309
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>
>
>
> --
> Best Regards,
>
> Wheat
> --
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