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Re: raw/block device disc troughput
On Thu, 24 May 2012, Thor Lancelot Simon wrote:
> On Thu, May 24, 2012 at 05:31:43PM +0000, Eduardo Horvath wrote:
> > With large transfers (larger than MAXPHYS) the writes are split up into
> > MAXPHYS chunks and the disk handles them in parallel, hence the
> > performance increase even beyond MAXPHYS.
> Is this actually true? For requests from userspace via the raw device,
> does physio actually issue the smaller chunks in parallel?
Depends... this case it's true. physio() breaks the iov into chunks and
allocates a buf for each chunk and calls the strategy() routine on each
buf without waiting for completion. So on a controller that does tagged
queuing they run in parallel.
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