8.1-STABLE: zfs and sendfile: problem still exists

[Andriy Gapon]

on 29/10/2010 17:53 Kostik Belousov said the following:
> Could it be the priming of the vm object pages content ?

Sorry, not familiar with this term.
Do you mean prepopulation of vm object with valid pages?

> Due to double-buffering, and (possibly false) optimization to only

What optimization?

> perform double-buffering when vm object already has some data cached,
> reads can prime vm object page list before file is mmapped or
> sendfile-ed.
> 

No double-buffering is done to optimize anything.  Double-buffering is a
consequence of having page cache and ARC.  The special "double-buffering code" is
to just handle that fact - e.g. making sure that VOP_READ reads data from page
cache instead of ARC if it's possible that the data in them differs (i.e. page
cache has more recent data).

So, if I understood the term 'priming' correctly, no priming should ever occur.

-- 
Andriy Gapon