Hi,
On Thu, May 18, 2000 at 08:16:30AM -0700, Dan Kegel wrote:
> While we're on the subject of raw I/O, I'd like to know whether using
> it wrong can cause low throughput.
>
> Is there anything inefficient about a worker thread sequentially
> using write() to a raw device on a bunch of areas in page order?
> For instance, the 'wait for write completion' prevents me from
> issuing the next write, and might lead to some noticable amount
> of idle time on the disk.
Absolutely. That's why we are working on async raw I/O APIs --- that
way you can submit multiple writes at once, allowing the driver to
coalesce them and pipeline them, while maintaining all of the cache
and synchronisation guarantees of raw I/O.
--Stephen
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