Re: ext2/3 performance regression in 2.6 vs 2.4 for small interl
From: John Bradford (john_at_grabjohn.com)
Date: 02/12/04
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Date: Thu, 12 Feb 2004 10:15:23 GMT To: Giuliano Pochini <pochini@shiny.it>, Andrea Arcangeli <andrea@suse.de>
Quote from Giuliano Pochini <pochini@shiny.it>:
>
> On 12-Feb-2004 Andrea Arcangeli wrote:
>
> > the main difference is that 2.4 isn't in function of time, it's in
> > function of requests, no matter how long it takes to write a request,
> > so it's potentially optimizing slow devices when you don't care about
> > latency (deadline can be tuned for each dev via
> > /sys/block/*/queue/iosched/).
>
> IMHO it's the opposite. Transfer speed * seek time of some
> slow devices is lower than fast devices. For example:
>
> Hard disk raw speed= 40MB/s seek time = 8ms
> MO/ZIP raw speed= 3MB/s seek time = 25ms
>
> One seek of HD costs about 320KB, while on a slow drive it's
> only 75KB.
Hmmm, but I would imagine that most hard disks have much larger caches
than are popular on removable cartridge drives...
John.
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- Previous message: Ingo Molnar: "Re: [BUG] get_unmapped_area() change -> non booting machine"
- In reply to: Giuliano Pochini: "Re: ext2/3 performance regression in 2.6 vs 2.4 for small interl"
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