On Mon, Jan 15, 2018 at 11:49 PM, kefu chai <tchaikov@xxxxxxxxx> wrote: > hey Casey, > > > i've been thinking about how to better integrate > seastar::temporary_buffer and seastar::packet into our denc and > messenger subsystems based on your wip-seastar-msg branch. > > as you pointed out to me that > >> the conversions between ceph::buffer::ptr and seastar::temporary_buffer in https://github.com/cbodley/ceph/tree/wip-seastar-msg/ work, but they cost an allocation in both directions (seastar::make_object_deleter() has to allocate for type erasure). > > and just like ceph::buffer::ptr, seastar::temporary_buffer also > manages the life cycle of the underlying memory chunk using refcount. > it's a waste to do the refcounting for the same mem chunk twice in the > same application. > > if we want to avoid the overhead of duplicated refcounting and > allocation in the conversion to and from ceph::buffer::ptr, i think, > we need to allocate the temporary_buffer along with buffer::ptr. in > other words, to include seastar::temporary_buffer as a member variable > in ceph::buffer:ptr. > > i am preparing a change to prototype this approach. the downside of it is: > > - we need to include a placeholder structure in buffer.h for > seastar::tempoary_buffer<char>. and cast it to > seastar::tempoary_buffer<char> in buffer.cc . otherwise we need to > include seastar headers in librados. - we cannot store the crc map along with the raw class anymore. this might be a show stopper. - we can not use zero copy interfaces anymore. but i think it's fine. as we need to use future/promise based interfaces for IO. > > cheers, > > > -- > Regards > Kefu Chai -- Regards Kefu Chai -- 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
