[Bug 3094] POOR I/O perfomance on VIA chipsets

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https://bugzilla.kernel.org/show_bug.cgi?id=3094





--- Comment #21 from Artem S. Tashkinov <t.artem@mailcity.com>  2010-05-19 17:17:37 ---
(In reply to comment #20)
> I/O wait is measuring the amount of time the machine is waiting for the disk,
> not how much it is using CPU. Disks haven't gotten much faster in the past ten
> years (SSD aside) while processors dramatically did. There isn't a lot that can
> be done about the speed of disks,. Getting the kernel to schedule I/O better
> can help a bit but the fundamental problem is that a disk on a good day can
> only really do about 200 operations/second.

What really enrages people (and me too) is that under all circumstances CPU
usage shown by `top` is always 100% whenever a single process is writing or
reading to a spinning storage at full speed.

It is _wrong_ and it is _misleading_ because then people think that the Linux
kernel sucks at I/O operations, everyone instantly recollects Windows
experience where (e.g. on my own PC) HDD access causes maximum 2% CPU usage.

Fix the kernel idle time computation, otherwise people will keep complaining
indefinitely.

`cat /dev/sda > /dev/null` results in load average rapidly climbing to 1.32 and
counting on my PC, that's just insane and wrong.

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