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SubjectRe: More on 2.2.18pre2aa2
On Tue, 12 Sep 2000, Rik van Riel wrote:

>Uhmmm, isn't the elevator about request /latency/ ?

Yes, but definitely not absolute "time" latency.

How do you get a 1msec latency for a read request out of a blockdevice
that writes 1 request in 2 seconds? See?

That was one of the first issues I was thinking about when I started
playing with the elevator. (and yes, some of my early patches was setting
a per-request timestamp using jiffies)

Note: I understand you can do in function of time something that works ok
for a normal 10/20Mbyte/sec harddisk, but since the elevator is used every
time you write to any blockdevice out there, you also have to take into
account things like ZIP drives and whatever other slow device that does
less than 1Mbyte/sec I/O or even slower (as well as faster devices). A zip
drive is slow writing, but that doesn't mean it isn't even slower while
seeking.

Andrea

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