Re: Special Kernel Modification

[Jeff Dike]

[e-mail] said:
> >  Mounting it synchronous will  disable caching in the VM.  
> Who told
> you that? Synchronous mounting turns off write buffering. Even with
> "-o sync" writes will still end up in the page cache, they'll just be
> commited immediately.

Ummm, how about O_DIRECT instead of O_SYNC (or maybe as well, my googling
hasn't been clear on whether O_DIRECT bypasses the cache on writes as well)?

All IO bypasses the virtual machine cache, so there's no multiple caching.

> Er, it will be shared in the host's context, but each VM will still
> have  their own copy in the page cache. This is no better than a
> COW'ed block device 

Nope.  You O_DIRECT here as well.

				Jeff