[Libguestfs] [PATCH nbdkit 0/7] server: Implement NBD_FLAG_CAN_MULTI_CONN.

[Richard W.M. Jones]

On Sat, Jan 05, 2019 at 01:19:50PM +0000, Richard W.M. Jones wrote:
> (2) I moved the locking to around calls to the sparse array code, and
> changed the thread model to parallel:
> 
>    read: IOPS=112k, BW=437MiB/s (458MB/s)(51.2GiB/120001msec)
>   write: IOPS=112k, BW=437MiB/s (458MB/s)(51.2GiB/120001msec)

FWIW I looked into this case with perf (25 GB of event data!) and
there are no obvious candidates for optimization unfortunately.  It's
about one third spent reading or writing to the Unix domain socket,
only about 4% waiting on locks, and the rest of the time either in fio
[the test program] or the kernel or doing actual work.

In other words, no easy wins ...

Rich.

-- 
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