On Wed, 18 Sep 2013, Rutger ter Borg wrote: > > Dear all, > > I've a question regarding buffers in rados (using the C++ API). I'm allocating > and using my own buffers, and would like to read and write directly into and > from them. I'm using a bufferlist consisting of static_buffers, which are > passed to Rados' aio_read and aio_write. > > For aio_write, rados works as expected, i.e., the bufferlist is returned as it > was before the call. However, when doing aio_read, it seems that the > bufferlist is destroyed (not used) in the call, despite all the buffers being > static. > > Is this expected behaviour? I read a thread "read/write on RADOS using > external buffer" from this mailing list from 2010, but wasn't able to figure > out whether rados does or doesn't support reading into user-provided > static_buffers. The read-into-existing-buffer is only wired up properly for the C interface. For the C++ it isn't generally necessary: we allocate and read the data off the network,a nd pass the reference directly back to the user without making another copy. The 2010 thread is about similarly avoiding such a copy for the C API. We didn't contemplate the situation where you specifically want the bytes to go to a particular address via C++. If that's what you need, the C++ API needs to be extended, or you can just use the C call for that case. 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
