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

Lawrence D'Oliveiro wrote:

On Mon, 12 May 2025 00:30:37 +0000, MitchAlsup1 wrote:
 

On Sun, 11 May 2025 23:46:17 +0000, Lawrence D'Oliveiro wrote:
>

That’s why we have memory caches.

>
Which architects tend to only understand what happens when these caches
are attached to CPUs and not "Joe Random Bus Master",

 One of my pet peeves is disk drives with memory caches in them. Why?
 

For reads it allows the disk to always read full sets of sectors, the following blocks are likely to be needed soon anyway.
For writes, as long as the drive has enough energy (maybe in the form of spinning inertia, or a hefty cap?) the always be able to save the buffer cache to spinning rust, it can allow operations to complete immediately, or as soon as the data has been transferred into the disk cache.
Since all disks are using linear sector (or 4K block?) addressing these days, instead of head/cylinder/sector, a little bit of cache can help hide the tiny time glitches when the disk has to reposition.
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"