Unmapped I/O

[Matthew Jacob]

On 12/19/2012 5:54 AM, Konstantin Belousov wrote:
> One of the known FreeBSD I/O path performance bootleneck is the
> neccessity to map each I/O buffer pages into KVA.  The problem is that
> on the multi-core machines, the mapping must flush TLB on all cores,
> due to the global mapping of the buffer pages into the kernel.  This
> means that buffer creation and destruction disrupts execution of all
> other cores to perform TLB shootdown through IPI, and the thread
> initiating the shootdown must wait for all other cores to execute and
> report.
>
About time!