Messages in this thread | | | Date | Fri, 19 Mar 1999 14:56:02 GMT | From | "Stephen C. Tweedie" <> | Subject | Re: disk head scheduling |
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Hi,
On Thu, 18 Mar 1999 20:50:36 +0100 (CET), Ingo Molnar <mingo@chiara.csoma.elte.hu> said:
>> Another point is that IN_ORDER seems to be called only for two requests >> on the same device, so no idea why it compares the device numbers.
To distinguish between partition access on the same major device.
> no, all requests (for all devices) are in a single 'queue'. (Per-major > device queues is candidate 2.3 feature, it's really simple)
No, each major has its own queue, defined either by the blkdev[major].queue() strategy function or by blkdev[major].current_request. As far as IN_ORDER is concerned, it will only ever look at one such queue at a time.
You're probably thinking of the global request array "all_requests", but that is just a global, static pool from which we allocate request structs. Active requests are most definitely kept on separate queues for each device.
--Stephen
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