[Info-vax] What would be involved in moving RMS into kernel mode ?

[Hein RMS van den Heuvel]

On Saturday, May 6, 2023 at 10:44:58 AM UTC-4, Arne Vajhøj wrote:
> On 5/6/2023 6:39 AM, Jan-Erik Söderholm wrote: 
> > About RMS Global Buffers. What files are these usually used for? 
> > I have got an (maybe wrong) impression that it is mostly indexed 
> > files "databases". 

Correct.

> But to provide value in the form of better performance then: 
> - the same file need to be accessed by multiple processes 
> - the access need to go through RMS 

Correct - with write sharing, so not useful for say SYLOGIN.COM.

One more requirement for performance gain through global buffers  is repeated access.
You also want to file to remain open as t5he established global buffers are dropped with the last accessor closing it.
One may go as far as creating a helper program to keep files open.

As an example repeated indexed file inserts would go through each index tree top to bottom and the top two layers can often be cached nicely.
With the 7.3 global buffer syslck method even a single process performing sequential gets to a shared file can benefit a lot.
Without global buffer each get would unlock the last record, lock the bucket, locate the next record, lock that, return it, unlock the bucket.
With Global buffers the bucket lock on happens on first entry into the bucket and thus saves almost half the lock activity.

One more easy global buffer win is cluster wide sharing. Whereas with single server access the XFC does a great job caching file, better than Global Buffers really as it is more dynamic, the XFC caching falls apart with cross cluster write shared access any write intend for a file from the 'other' node will flush the buffers for that file everywhere else. The other node then starts building its cache for the file only to tapped on the should for a flush a couple of buffers into the process. RMS Global buffer to NOT have this issue as each buckets is protected from being stale through a per-bucket lock, not per file.

And yes, the classic 'thick', 'cobol' application is a prime candidate but think also about SYSUAF.DAT, RIGHTSLIST.DAT,...

Cheers,
Hein.