FUJITA Tomonori wrote:
On Tue, 22 Jan 2008 14:33:13 +0300
Vladislav Bolkhovitin <vst@xxxxxxxx> wrote:
FUJITA Tomonori wrote:
The big problem of stgt iSER is disk I/Os (move data between disk and
page cache). We need a proper asynchronous I/O mechanism, however,
Linux doesn't provide such and we use a workaround, which incurs large
latency. I guess, we cannot solve this until syslets is merged into
mainline.
Hmm, SCST also doesn't have ability to use asynchronous I/O, but that
doesn't prevent it from showing good performance.
I don't know how SCST performs I/Os, but surely, in kernel space, you
can performs I/Os asynchronously.
Sure, but currently it all synchronous
Or you use an event notification
mechanism with multiple kernel threads performing I/Os synchronously.
Xen blktap has the same problem as stgt. IIRC, Xen mainline uses a
kernel patch to add a proper event notification to AIO though redhat
uses the same workaround as stgt instead of applying the kernel patch.
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