Changing location of disk/filesystem cache

[Mandeep Sandhu]

On Thu, Oct 10, 2013 at 5:00 PM, Ulka Vaze <ulka.vaze at l2it.com> wrote:

> Hi,
> disk cache is same as filesystem  cache. Also called buffer cache.
> This is implemneted below fs layer.
> It is basically a cache of disk blocks  mainatined in RAM. (In pages)
> called buffers.
>

Ok. So this won't contain "files" but rather "blocks" many of which will
represent a single file?


> The purpose of this cache is to improve performance as disk devices are
> slow.
> You can access this cache from the kernel.
> Block layer accesses this from the request structure and commits blocks on
> disk.
> There are more layers in between like IOschedulers / SCSI etc.
>

Where does the mapping for file to disk pages/blocks exist? Is it in the
inode or dentry entries or something else?


>
> How  does your device accesses files ?
>

The device itself runs stripped down version of a fairly recent Linux
version (3.x). It has DMA capabilities to transfer content to/from the
hosts memory from/to it's own.


> Is it aware of files or you just copy raw data.
>

It can understand both.


> More clarity on this can help.
>

Thanks for your inputs.

Regards,
-mandeep
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