[haiku-development] Re: gsoc2010: File systems
- From: Ingo Weinhold <ingo_weinhold@xxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Thu, 01 Apr 2010 11:47:44 +0200
On 2010-04-01 at 10:29:43 [+0200], Axel Dörfler <axeld@xxxxxxxxxxxxxxxx>
wrote:
> Janito Ferreira Filho <jvffprog@xxxxxxxxxxx> wrote:
> > does the block cache and file cache operate in a similar fashion to
> > the
> > Linux buffer and page cache? If so, the unification would then be to
> > use
> > the file cache to manage the VM structures and the block cache would
> > be based on the file cache?
>
> I'm afraid I'm not familiar enough with Linux to answer that one.
> How the unification works is still a bit blurry to me, as I haven't
> given it too much thought yet; maybe Ingo has done more in this regard
> already ;-)
No, it's a rather vague idea ATM. Basically once the file cache supports
transactions, using a file cache on top of a block device would already
come pretty close to what a block cache has to do. Moreover Haiku's file
systems generally also allow mounting files (instead of just block
devices), in which case we already have a file cache at hand. And finally
using a VMCache backing also for block devices would give us a better
integration with the VM, allowing us to mmap() block devices and resulting
in a more balanced reuse of cached data and meta data.
The major difference between file and block cache is the API used by the
file system. The block cache strictly works with block sized units and
needs to (temporarily) map them into memory. It needs to handle both block
sizes less than, equal to, and greater than the page size.
ATM I see no problem in principle, but the idea needs to be fleshed out
more in detail.
CU, Ingo
Other related posts:
