[RC5] LIFO? Is this true?

gindrup at okway.okstate.edu gindrup at okway.okstate.edu
Thu May 7 19:33:18 EDT 1998


     And at the time these architectural decisions were made, 10 minutes 
     was important.  First, there were no clients then.  Optimizing the 
     cores was still giving ~30% improvements per revision.  Stabilizing 
     the network code was critical.
     
     Spending 10 minutes in these areas was much more productive than 
     worrying about FIFO vs. LIFO in the buffer structure.
     
     On a semi-related note...
     It recently struck me that there would be better symmetry if instead 
     of checkpointing, partial blocks were written to the buff-out and 
     blocks in the buff-in weren't deleted until all of their subparts 
     were in the buff-out.  The symmetrical relation is to that of the 
     subspaces not being marked as done until all the little blocks in 
     them are marked as done...  As a coding detail, I would set this up 
     in the same way that requested blocks are set up: what's the log 
     (base 2) of the number of keys you want in a checkpointing write to 
     the buff-out?  The buff-in would fluff out to allow all the little 
     block parts to be represented separately.  Partially completed 
     blocks would need to be selected preferentially to entirlely 
     untouched blocks.  Blocks should be (or possibly already are) 
     datestamped and old blocks should receive preference.
     
     Of course, this makes the buff files again incompatible...
            -- Eric Gindrup ! gindrup at okway.okstate.edu


______________________________ Reply Separator _________________________________
Subject: Re: [RC5] LIFO?  Is this true? 
Author:  <rc5 at llamas.net> at SMTP
Date:    5/7/98 3:00 PM


At 11:51 AM 5/6/1998 , Jim C. Nasby wrote:
>It was designed this way because most operating systems don't readily 
>support FIFO files, and LIFO is much easier to impliment from a coding 
>standpoint. Have no fear, v3 will be FIFO... :)
>
>Mooo!
>dB!
     
Well... Most operating systems don't support LIFO either.  They support 
sequential reads/writes and positioning to a specific byte offset.  FIFO 
takes about 10 minutes of extra coding compared to LIFO.
     
- Sanford
     
     
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