Delayed writes on removed files

[Dale Farnsworth]

Amos Shapir (amos at taux01.UUCP) writes:
> Here is something new  for a change: When a file  is removed, its blocks
> are released to  the free list. If  any writes were done,  some of these
> blocks may  still be in  the buffer pool,  waiting for a  delayed write.
> When such  buffers are reallocated,  they will  be written to  the disk,
> even though their contents are no longer relevant.
> 
> The systems I have checked - 4.2  and sysV.3 - make no effort to prevent
> this. It seems  that in an environment in which  many files are created,
> written to, and then discarded (e.g. compilation) preventing unnecessary
> writes  to  disk  may  have  a  significant  effect  on  overall  system
> performance. Does anyone know of a system that does this, and how?

Yes, a few years ago we made the same observation.  When blocks belonging
to a file are removed, the cached block list is searched and any blocks
belonging to the file are moved to the front of the queue (to be allocated
next) and any delayed write flags are cleared.

-Dale

-- 
Dale Farnsworth		602-438-3092	uunet!unisoft!nud!df