Re: OT: What is this Intel Parallel Studio?

On Tue, 24 Nov 2009 14:58:31 +0000, Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

JosephKK wrote:
On Sat, 21 Nov 2009 13:04:04 +1100, Sylvia Else
<sylvia@xxxxxxxxxxxxxxxxxxx> wrote:

Archimedes' Lever wrote:
On Fri, 20 Nov 2009 17:00:26 -0800, "Joel Koltner"
<zapwireDASHgroups@xxxxxxxxx> wrote:

"Nobody" <nobody@xxxxxxxxxxx> wrote in message
news:pan.2009.11.21.00.34.28.469000@xxxxxxxxxxxxxx
That's only an issue if you're saturating the memory bandwidth, and
there are plenty of applications which don't.

My impression that it's actually rather few of them!

So use a solid state drive as your virtual memory volume.

How would that help?

It would make the swap / virtual memory operate at near memory speeds,
instead of the 100,000 times slower disk speeds. Of course just using
more RAM is often cheaper and more effective (eliminate the need for
swap entirely and remove it).

I am afraid it wouldn't help that much even with a RAID0 array of SSD.
The seek time is very much better than a physical platter drive but you
are still limited by the external bus transfer rate which is typically
for sustained activity on an SSD about 250MBps read and half that for
writes. The latter hurts in a virtual memory swap file application.

They are magic for random lookups of multigigabyte datasets though.

Regards,
Martin Brown

Yes, and how much do you get out of a swap volume (not normally
RAIDable)? 50 MB/s? (sequential read, and how much of that occurs)
and do remember that random (to the disk) reads, which may be
frequent, incur head movement overhead of milliseconds. In SSD this
is microseconds.
Just reinforces my preference for more RAM instead.
Of course there is the write lifetime issue for SSD as well, if used
as swap, life could be on the order of months.
.

Relevant Pages

  • Re: [rfc] no ZERO_PAGE?
    ... For purely-RAM virtual memory the latency ... disk if you add swap to the picture. ... is slower, ram is faster. ...
    (Linux-Kernel)
  • Re: Mac Mini virtual memory question
    ... Mac OS X automatically allocates hard disk space to virtual memory as ... required (by creating more swap files). ... swap files are only created as necessary to hold the parts ...
    (comp.sys.mac.system)
  • Re: Which partitioning scheme gives best performance?
    ... >> swap and doesn't release it. ... The 2*RAM for swap was *never* a rule of thumb for Linux, ... RAM was also allocated an equal amount of swap. ... there was no virtual memory. ...
    (comp.os.linux.misc)
  • Re: Which partitioning scheme gives best performance?
    ... >> swap and doesn't release it. ... The 2*RAM for swap was *never* a rule of thumb for Linux, ... RAM was also allocated an equal amount of swap. ... there was no virtual memory. ...
    (comp.os.linux.setup)
  • Re: Intel 160 GB ssd drive now $425
    ... It's not as if pages jump back and forth between swap and main memory continuously. ... They do when there is a significant shortage of system ram. ... Your claim about an SSD being a lot cheaper is just plain mindlessly silly. ...
    (comp.sys.ibm.pc.hardware.storage)