user defined cache

user defined cache

[Warwick Boote]

Hi all,

Do you know of setting or layered file system that enables me to define
a large buffer in main memory and cache writes to this buffer?

Obviously i'd need the file system to also read from this buffer if the
data hasn't been flushed to the disk yet.


Waz.
=)




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Re: user defined cache

[Mark]

--- On Thu, 7/3/08, Warwick Boote <wboote@civica.com.au> wrote:
> Hi all,
> 
> Do you know of setting or layered file system that enables
> me to define
> a large buffer in main memory and cache writes to this
> buffer?
> 
> Obviously i'd need the file system to also read from
> this buffer if the
> data hasn't been flushed to the disk yet.

XFS supports the following mount options, and they do 
increase throughput somewhat on my system:

logbufs=N (helps concurrency)
logbsize=N (helps log buffering)

If you are using an internal XFS log, you may also try 
"nobarrier" to reduce force-to-disk write frequency. 
NB: I have seen this option discussed on this mailing 
list, but I do not see it in the mount(8) man page.

Bear in mind that the XFS log is for metadata, rather than 
actual file data. This may be what you're looking for, or at
least sufficient; if not, my apologies.
-- 
Mark

"What better place to find oneself than
 on the streets of one's home village?"
      --Capt. Jean-Luc Picard, "Family"

Re: user defined cache

[Dave Chinner]

On Fri, Jul 04, 2008 at 12:40:05PM +1000, Warwick Boote wrote:
> Hi all,
> 
> Do you know of setting or layered file system that enables me to define
> a large buffer in main memory and cache writes to this buffer?

I know there's wrapper libraries that do this - like FFIO -
but I don't think there's a free one.

However, why doesn't the page cache do what you want already?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com