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Choosing Dual or Quad Core

23 replies on 2 pages. Most recent reply: Sep 16, 2007 11:52 PM by Jeroen Wenting

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Flat View: This topic has 23 replies on 2 pages [ « | 1 2 ]

James Watson

Posts: 2024
Nickname: watson
Registered: Sep, 2005

Re: Choosing Dual or Quad Core

Posted: Sep 5, 2007 8:53 AM

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> Sorry, I went onto a theoretical tangent and didn't
> address the specific problem you mentioned. I don't have
> my copy of MOS handy, so I can't check and see if Prof.
> Tanenbaum addresses this issue. If the explanation you've
> heard is accurate, it seems like shaky reasoning. I'll
> have to think about that one for a little longer.

I was just looking at my task manager and it shows more than a GB of free physical memory. When I look at the VM sizes of all processes, they definitely don't add up to a GB. Maybe a little over 500MB. I'm no OS expert but I can't seem to come up with a good explanation for this behavior. Why page when you have tons of free RAM?

James Watson

Posts: 2024
Nickname: watson
Registered: Sep, 2005

Re: Choosing Dual or Quad Core

Posted: Sep 5, 2007 8:54 AM

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Oh yeah, I once found some instructions on how to prevent this behavior but they were prefaced with a stern warning about how it could cause system instability and could crash windows.

Bill Pyne

Posts: 165
Nickname: billpyne
Registered: Jan, 2007

Re: Choosing Dual or Quad Core

Posted: Sep 5, 2007 9:42 AM

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> I was just looking at my task manager and it shows more
> than a GB of free physical memory. When I look at the VM
> sizes of all processes, they definitely don't add up to a
> GB. Maybe a little over 500MB. I'm no OS expert but I
> can't seem to come up with a good explanation for this
> behavior. Why page when you have tons of free RAM?

Okay, from the little reading I've been able to do during lunch today, it looks like a design choice was made to reserve a percentage of RAM for the startup of applications not already loaded. By doing so, the designers insure that an application just starting - presumably the app. the user is most concerned with using at the time - doesn't incur a double cost of being loaded and being swapped (or an already loaded app. being swapped which is more likely). Again, I lack any background in OS design so look on what I write with a very skeptical eye.

Mark Thornton

Posts: 275
Nickname: mthornton
Registered: Oct, 2005

Re: Choosing Dual or Quad Core

Posted: Sep 6, 2007 4:24 AM

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> One of the apps that consistently made my old XP system
> comatose was Eclipse. If it was idle for a while, bringing
> it out of dormancy would effectively stop use of the
> system until it was finished. My guess is it had to do
> with the JVM; I think I even read a article about it a few
> years back.

When you minimise an application, Windows sets its working set to zero. This means that its pages are then prime candidates to be paged out. Some applications override this behaviour to gain better performance for themselves.

Bill Pyne

Posts: 165
Nickname: billpyne
Registered: Jan, 2007

Re: Choosing Dual or Quad Core

Posted: Sep 6, 2007 6:32 AM

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> When you minimise an application, Windows sets its working
> set to zero. This means that its pages are then prime
> candidates to be paged out. Some applications override
> this behaviour to gain better performance for themselves.

Thanks! It makes more sense now and seems to follow the design goals I believe the XP team had and that James has mentioned: keeping a certain amount of RAM free at all times.

Having Eclipse paged is partly my own fault. With most applications I'm still old school about shutting them down after each use. With my development tools, leaving them open between coding sessions allows me to rebuild the program in my head quicker. I can't expect an OS design team to cover every use that every user has.

Cameron Purdy

Posts: 186
Nickname: cpurdy
Registered: Dec, 2004

Re: Choosing Dual or Quad Core

Posted: Sep 10, 2007 11:14 AM

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> My comment is going to be more from the perspective of a
> user of desktop applications than a developer. Rarely do I
> pin the cpu even on a single cpu system. More commonly I
> get pauses (the spinning beach ball on Mac OS X or the
> comatose system on Windows XP) from high disk activity.
> Multi-cores are currently the latest, sexy topic in IT,
> but I think we'd see much better performance from a
> solution to the disk crunching that occurs on every
> desktop I've worked on (Windows, Linux, Mac).

It's coming. Solid state disks (or hard disks augmented with flash storage) will almost certainly change the way desktop and notebook users think about disk I/O. At the current pace, within a few years 250GB solid state disks with >100MB/s transfer rates and instant seek times will be common-place.

Regarding multi-core processors, not even thinking about the "speed" benefit, every software engineer should be using them today, since they make it a lot easier to encounter threading problems, and if software is going more and more parallel, it would be nice if those problems got noticed earlier than later.

As for needing the horsepower, I often have both my cores on my notebook pegged, but you're right - I'd personally rather have a faster hard drive than any more cores right now.

Peace,

Cameron Purdy | Oracle
http://www.oracle.com/technology/products/coherence/index.html

Bill Pyne

Posts: 165
Nickname: billpyne
Registered: Jan, 2007

Re: Choosing Dual or Quad Core

Posted: Sep 12, 2007 6:38 AM

Reply

> It's coming. Solid state disks (or hard disks augmented
> with flash storage) will almost certainly change the way
> desktop and notebook users think about disk I/O. At the
> current pace, within a few years 250GB solid state disks
> with >100MB/s transfer rates and instant seek times will
> be common-place.

I'm sure Oracle is already playing with some of this technology in its R&D wing and that they're noting architectural changes to their DBMS that will be possible. (Between their acquisition of an in-memory database line and solid state disks, the DBMS should go to a new level of performance and reliability.) So, I'll take your word that it's coming.

Roberto Martino

Posts: 3
Nickname: chairam
Registered: Feb, 2007

Re: Choosing Dual or Quad Core

Posted: Sep 13, 2007 4:33 PM

Reply

> It's coming. Solid state disks (or hard disks augmented
> with flash storage) will almost certainly change the way
> desktop and notebook users think about disk I/O. At the
> current pace, within a few years 250GB solid state disks
> with >100MB/s transfer rates and instant seek times will
> be common-place.

My pc has 2Gb. It is a quite appropriate amount to my needs, but can feel the difference when my applications use more than 1Gb. The idea is simple: let me add as much ram as i want (on a pci board?) that the operating system can use as disk cache or ram disk, say 4, 8, 16Gb or more, let me choose.
Couldn't this be a solution? (I know there is something similar in vista using usb pens, but 32Gb of ram are different from a 4Gb usb pen)

Jeroen Wenting

Posts: 88
Nickname: jwenting
Registered: Mar, 2004

Re: Choosing Dual or Quad Core

Posted: Sep 16, 2007 11:52 PM

Reply

> > If you benchmark using only one application, the
> results
> > probably won't indicate much improvement, but what
> happens
> > if you play a video, while browsing the net and work
> with
> > photoshop at the same time?
>
> Playing a video while browsing and working in Photoshop
> would indeed be CPU intensive, but is it realistic? I'm
> not trying to be flippant, I just don't understand how
> someone would simultaneously do all three. I could
> understand if you're talking about a server that multiple
> people are simultaneously demanding services of.
>

yes, it (or similar scenarios) can be quite realistic (depending on what you're doing of course).

I've done some work creating addons for MS Flight Simulator.
This usually means running MSFS, Photoshop, one or two web browsers (for technical forums etc.), maybe a 3D modelling application, and some tools. As you're constantly switching between them it makes little sense opening and closing applications all the time (especially as those applications can take several minutes to load).

MSFS alone can easily top out a CPU, and the latest version can top out both cores on a dual core system (previous versions weren't coded to benefit from multicore machines).
It may be a niche market, but the requirement can certainly exist.

> I could see high end video production editors having to
> edit multiple clips in different windows or video game
> designers having multiple game windows running in
> parallel. I would hazard a guess that they cover less than
> 1% of all desktop users.

Most certainly, but so do developers as a group (not counting schoolkids and students doing homework for their courses, they don't have the requirements for long).

That doesn't however mean that there's no use for quad (or higher) number of cores in the current market even if software doesn't make use of them.
It just means that most people who purchase quad core machines will not at the moment use them to full capacity (but very well may in the future once software adapts to make use of them).

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