Linux tmpfs (Was: [OpenAFS] Solaris 10u6: ZFS cache?)

[Christof Hanke]

While talking about cache-performance (not that I know how they really work=
)
Would it be beneficial to have a separate Meta-data cache from a File-data =
cache?
I'm thinking of situations where the the performance is poor (long distance=
, whatever)
It would me frustrate a lot, if I had to wait, say 10 min, for an "ls" and =
after downloading a file bigger than my cache another "ls" would
take the same time.
So, would it make sense to cache the stat() information in a separate cache=
 ?
Just thinking loud here.

Christof
________________________________________
From: openafs-info-admin@openafs.org [openafs-info-admin@openafs.org] On Be=
half Of Brandon S. Allbery KF8NH [allbery@ece.cmu.edu]
Sent: Friday, November 14, 2008 8:28 PM
To: Chas Williams
Cc: Brandon S. Allbery KF8NH; Jason Edgecombe; Harald Barth; deengert@anl.g=
ov; shadow@gmail.com; openafs-info@openafs.org
Subject: Re: Linux tmpfs (Was: [OpenAFS] Solaris 10u6: ZFS cache?)

On 2008 Nov 14, at 7:18, Chas Williams (CONTRACTOR) wrote:
> In message <5FB03AFA-8CA1-4B39-
> A743-188E5DBF4666@ece.cmu.edu>,"Brandon S. Allbe
> ry KF8NH" writes:
>> It used to be said (back when warlord was maintaining linux-afs and
>> Transarc 3.4a was the main release) that the memcache was much less
>> efficient than the disk cache and that it was better to use disk
>> cache
>> in a ramdisk.  Both have been pretty thoroughly overhauled since
>> then,
>> though.
>
> "efficient" isnt meaningful without context.  memcache does use quite
> a bit of host memory.  if your system is short on memory, memcache is
> not for you.  however, memcache outperforms diskcache is most cases
> (ignoring say rereads over a link with high latency).

At the time memcache was an unoptimized linked list, IIRC, and
performance simply stank.  It was worse than disk cache.

--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH


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