On Wednesday, October 20, 2010, Andreas Dilger wrote: > On 2010-10-20, at 10:40, Michael Kluge <[email protected]> wrote: > > It is the CPU load on the client. The dd/IOR process is using one core > > completely. The clients and the servers are connected via DDR IB. LNET > > bandwidth is at 1.8 GB/s. Servers have 1.8.3, the client has 1.8.3 > > patchless. > > If you only have a single threaded write, then this is somewhat unavoidable > to saturate a CPU due to copy_from_user(). O_DIRECT will avoid this. > > Also, disabling data checksums and debugging can help considerably. There > is a patch in bugzilla to add support for h/w crc32c on Nehalem CPUs to > reduce this overhead, but still not as fast as no checksum at all.
I think checksums are only visible in ptlrpc CPU time (and most also only for reads), but not in the user space benchmark process. Cheers, Bernd -- Bernd Schubert DataDirect Networks _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
