DaemonForums  

Go Back   DaemonForums > DaemonForums.org > News

News News regarding BSD and related.

Reply
 
Thread Tools Display Modes
  #1   (View Single Post)  
Old 22nd February 2010
J65nko J65nko is offline
Administrator
 
Join Date: May 2008
Location: Budel - the Netherlands
Posts: 4,125
Default Update on tmpfs and swapcache work (in master)

Matthew Dillon in a post to the DragonFlyBSD users mailing list
Quote:
Subject: Update on tmpfs and swapcache work (in master)
Group: Dragonflybsd-users
From: Matthew Dillon
Date: 20 Feb 2010


I've nailed a few more bugs in tmpfs, including one that caused
excessive paging to swap, a VM object leaking in kernel virtual memory
(try to imagine that visually <grin>), and stomped a few bug reports
related to fsstress tests Venkatesh ran.

tmpfs is now working very nicely with memory & swap, with minimal
paging to swap when memory is available to hold the data. It is
starting to look like it will be a very good fit against SSD-based
swap and swapcache, and frankly tmpfs should work well with HD-based
swap too.

--

swapcache is also faring very well in all tests done so far, for
those people interested inconfiguring Solid State Drive (SSD) based
swap space. The manual page has been updated and the data caching
capability has gotten a little more sophisticated with the new
chflags flags.

Some tuning with disklabel64 (for labeling the SSDs) has been done to
align the partition base and reduce write amplification and write
combining effects by the SSD drive firmware. Swapcache also does a
pretty good job clustering and linearizing write operations.

I am running ongoing tests on pkgbox64 with one of these Intel X25-V
40G SSDs with 32G of swapcache configured and so far I haven't even
managed to tick over the wear meter. It started at 99% and it's
still 99% after 569GB worth of intentionally heavy write activity.

The X25-V has a stated write durability of around 40TB but with
static wear leveling MLC cells theoretically have a 10,000 erase
cycle endurance which would be more around 400TB. The Intel SSD
apparently does a combination of static and dynamic wear leveling.
A key point here is the swapcache is laying down data very efficiently
compared to what a filesystem-on-SSD would do, and this should result
in significantly less write amplification than we would otherwise expect.

My expectation is we could get upwards of 150-250TB of write durability
out of this particular device. I won't know for probably another week
or two at the rate pkgbox64 is currently writing but if it turns out to
be true then MLC-based SSDs will be totally viable at higher write
bandwidths.

-Matt
Matthew Dillon
<dillon>
Source: http://readlist.com/lists/lists.drag...rs/1/8610.html
__________________
You don't need to be a genius to debug a pf.conf firewall ruleset, you just need the guts to run tcpdump
Reply With Quote
  #2   (View Single Post)  
Old 22nd February 2010
J65nko J65nko is offline
Administrator
 
Join Date: May 2008
Location: Budel - the Netherlands
Posts: 4,125
Default

In an earlier post Matt explains the features of tmpfs
From http://readlist.com/lists/lists.drag...rs/1/8600.html:

Quote:
Subject: tmpfs now operational in development branch
Group: Dragonflybsd-users
From: Matthew Dillon
Date: 16 Feb 2010

We now have a very nice port by Naoya Sugioka of TMPFS from NetBSD
in our main development branch. It is brand new and still considered
experimental but should be reasonably stable.

TMPFS is a better alternative to MFS and MD for temporary filesystems.
It doesn't have the data duplication issue that MFS has and its data
is swap-backed using a very nice algorithm that only pages data to swap
when the system is under real memory pressure (and not due to buffer
cache flushes, fsyncs, or anything else).

-Matt
Matthew Dillon
<dillon>
__________________
You don't need to be a genius to debug a pf.conf firewall ruleset, you just need the guts to run tcpdump
Reply With Quote
Reply

Tags
ssd

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Understanding Fdisk, Slice, and the MBR (Master Boot Record) FBSD Guides 1 20th February 2010 08:33 PM
DragonFly BSD MPSAFE progress and testing in master J65nko News 0 29th December 2009 02:50 AM
Installation master "disk" using USB memory stick, dd? peterg22 FreeBSD Installation and Upgrading 7 14th October 2008 05:18 PM
installworld fails - because I deleted master.passwd? TomAmundsen FreeBSD Installation and Upgrading 4 22nd September 2008 07:51 PM
Getting Qt4 to work on FreeBSD enpey FreeBSD Ports and Packages 6 6th May 2008 07:20 AM


All times are GMT. The time now is 07:07 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Content copyright © 2007-2010, the authors
Daemon image copyright ©1988, Marshall Kirk McKusick