Re: Is Parallel Programming Hard, And, If So, What Can You Do About It?

On 5/19/2025 1:46 PM, Vir Campestris wrote:

On 19/05/2025 02:41, Stephen Fuld wrote:

>
It didn't make sense to, after executing the full track read, since the disk was positioned at the end of the track, and you had a good indication that it was a sequential file read, to start caching the next track in anticipation of the next full track read?

 It might if the disk was idle. But if there is a queue from another process it probably will be better to do that instead.

I presume you know that the 3880 controller did not do what today we call command queuing, so I think you were referring to a potential queue in the host.  That being the case, the controller doesn't know if there is a queue or not.  So given that, why not start reading record 1 on the next track.  If a request comes in, you can abandon the read to service the request - no harm, no foul.  If there isn't, and you subsequently get a request for that track, it's a big win.  The only potential loss is if you get a request for the track that was LRU and got pushed out of the cache.
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  - Stephen Fuld
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