On Fri, 11 Feb 2011 09:47:17 -0500, Jan Kara <jack@xxxxxxx> wrote:
On Sun 06-02-11 10:13:41, Sorin Faibish wrote:
I was thinking to have a special track for all the writeback related
topics.
Well, a separate track might be a bit too much I feel ;). I'm
interested
also in other things that are happening... We'll see what the program
will
be but I can imagine we can discuss for a couple of hours but that might
be
just a discussion in a small circle over a <enter preferable drink>.
No problem. I pay for the beer. :) You make the expert pick.
I would like also to include a discussion on new cache writeback paterns
with the target to prevent any cache swaps that are becoming a
bigger problem
when dealing with servers wir 100's GB caches. The swap is the worst
that
could happen to the performance of such systems. I will share my
latest findings
in the cache writeback in continuation to my previous discussion at
last LSF.
I'm not sure what do you exactly mean by 'cache swaps'. If you mean
that
your application private cache is swapped out, then I can imagine this
is a
problem but I'd need more details to tell how big.
What I meant is to prevent any global cache swap. Think that you have to
SWAP
256GB of cache to a 120MB/sec SATA disk. How long it will take? Cannot be
tolerated. Even if you use SSD at say 1GB/sec it is still a long time. Not
typical but common in HPC. I am not sure you saw my latest results but I
had an example where the swap was taking a long time to the point that a
build on a small memory system didn't finish. The good news are that the
latest kernels 37 RC3 made progress. I have additional data to present.
I will present the latest results next week at FAST conference.
/Sorin
Honza
--
Best Regards
Sorin Faibish
Corporate Distinguished Engineer
Unified Storage Division
EMC²
where information lives
Phone: 508-249-5745
Cellphone: 617-510-0422
Email : sfaibish@xxxxxxx
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