<div dir="ltr"><br><div class="gmail_extra"><div class="gmail_quote">On Thu, Oct 10, 2013 at 5:00 PM, Ulka Vaze <span dir="ltr"><<a href="mailto:ulka.vaze@l2it.com" target="_blank">ulka.vaze@l2it.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
disk cache is same as filesystem cache. Also called buffer cache.<br>
This is implemneted below fs layer.<br>
It is basically a cache of disk blocks mainatined in RAM. (In pages)<br>
called buffers.<br></blockquote><div><br></div><div>Ok. So this won't contain "files" but rather "blocks" many of which will represent a single file? <br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
The purpose of this cache is to improve performance as disk devices are slow.<br>
You can access this cache from the kernel.<br>
Block layer accesses this from the request structure and commits blocks on disk.<br>
There are more layers in between like IOschedulers / SCSI etc.<br></blockquote><div><br></div><div>Where does the mapping for file to disk pages/blocks exist? Is it in the inode or dentry entries or something else?<br></div>
<div> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
How does your device accesses files ?<br></blockquote><div><br></div><div>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.<br>
</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Is it aware of files or you just copy raw data.<br></blockquote><div><br></div><div>It can understand both.<br> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
More clarity on this can help.<br></blockquote><div><br></div><div>Thanks for your inputs.<br><br></div><div>Regards,<br></div><div>-mandeep<br><br></div></div></div></div>