Re: squid and tcp splicing ?

From: J.Smith <>
Date: Wed, 10 Sep 2003 23:20:47 +0200

----- Original Message -----
From: "Henrik Nordstrom" <>

> But there is other complications as well even if we stay HTTP/1.0.
Ok. I guess that this means that there still is a lot of room for further
research left in this area, and we just aren't there yet for real world
applications. Maybe I should just stop reading those research papers...

> It is my opinion that there is many better ways of optimizing proxy
> class I/O without resorting to kernel level "splicing". For example
> it would be very interesting to see a I/O mechanism not involving
> copying of data on each read/write combined with a sane event
> notification. This would accomplish the same goal with fully
> preserved semantics and only marginally increased CPU load compared
> to kernel level "splicing".

Well at least we seem to agree on the fact that the context switches and
data copy caused by application-level transfers results in performance loss,
and that this could be addressed.

> (AIO has reasonable I/O primitives but lacks in notification,

Well as far as I can tell, asynchronously notifying the I/O completion in
AIO is accomplished by sending signals, and an application may request that
a SIGIO signal be delivered when the I/O operation is complete. If several
requests have been issued, the application can poll the status of the
requests to determine which ones have actually completed. From your message,
I gather that this is not sufficient ? I vaguely seem to remember some
issues (regarding the reliable delivery ?) when using signals in combination
with threads.


John Smith
Received on Wed Sep 10 2003 - 21:22:27 MDT

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