Computers are fast • Hacker News Board

Re: Computers are fast

#31

Post by alecco » Tue, Oct 12, 2010, 9:31 PM UTC

jjcm wrote: post #29

alecco wrote: post #13

CPUs are fast but the ratio of latency of random access vs. maximum bandwidth is getting worse. In nanoseconds, approximately: 10^7 Disk seek 10^4 2KB over 1Gbps 10^2 RAM uncached reference 10^1 L2/L3 cache reference 10^0 L1 cache reference That's why systems don't feel fast lately. In particular for big data or bloated software that can't fit well within the caches or shared systems doing a lot of frequent switches…

SSD's have become viable in terms of $/GB to justify them in a server room these days. I'd highly recommend moving to them (for your boot drive/VMs at least). It will make a world of difference. $400 may seem like a lot to spend for 160GB of storage, but knocking off two orders of magnitude off your seek time quickly becomes worth it when you're running four VMs off it at once.

Seagate Momentus XT hybrid is very cool. Probably the best bang for the buck at the moment.

http://www.anandtech.com/show/3734/seagates-momentus-xt-revi...

Re: Computers are fast

#32

Post by jacquesm » Tue, Oct 12, 2010, 9:38 PM UTC

GeoKangas wrote: post #24

yan wrote: post #11

Something I like thinking about: Your computer can (probably) perform a few dozen arithmetic operations or a few stores/reads in the time light leaving your monitor takes to reach your eye balls. edit: not to mention GPUs

I don't think so. Light travels about 1 foot/nanosecond, so the travel time from monitor to eyeball is 1 or 2 nanoseconds, which might be 2 or 3 clock cycles. So I think at most 3 operations per CPU.

That's your foot though, mine is smaller.

Re: Computers are fast

#33

Post by jacquesm » Tue, Oct 12, 2010, 9:41 PM UTC

If computers are so fast how come I'm waiting for them as much as ever?

Re: Computers are fast

#34

Post by ed » Tue, Oct 12, 2010, 9:41 PM UTC

This is why we can't have nice things!

I'm kidding, obviously, but this is a very common phenomenon. Developers optimize their algorithms based on real-world performance instead of theory.

I wonder what impact this has on the world, would the cost of computing be dramatically lower (making computers more accessible) if we didn't do this?

Re: Computers are fast

#35

Post by TeHCrAzY » Tue, Oct 12, 2010, 10:36 PM UTC

yan wrote: post #21

woadwarrior01 wrote: post #18

Earlier quoted context omitted.

I just had to do arithmetic. A 3 GHz processor would clock about 10.006671 cycles in the time it takes for light to travel 1 meter.

Current Intel Core CPUs have 3 ALUs/core and 2 cores..

The high end core 7's are up to 6 cores now.

Re: Computers are fast

#36

Post by TeHCrAzY » Tue, Oct 12, 2010, 10:40 PM UTC

senki wrote: post #23

potatolicious wrote: post #19

Earlier quoted context omitted.

Sometimes I wonder if the OS can put very heavily used files from the FS into RAM. Some software just sucks and keeps pulling the same files over and over... ... and the plus side is, if an application needs the RAM, no harm done, just dump the file from RAM and read it from disk.

Good idea. They already do it.

Specifically: SuperFetch, first seen in Vista: http://en.wikipedia.org/wiki/Windows_Vista_I/O_technologies#...

Re: Computers are fast

#37

Post by extension » Tue, Oct 12, 2010, 10:53 PM UTC

Naturally, when writing a non-realtime program that is only going to be run once, you should consider development time to be part of running time.

Re: Computers are fast

#38

Post by silentbicycle » Tue, Oct 12, 2010, 11:57 PM UTC

TeHCrAzY wrote: post #36

senki wrote: post #23

Earlier quoted context omitted.

Good idea. They already do it.

Specifically: SuperFetch, first seen in Vista: http://en.wikipedia.org/wiki/Windows_Vista_I/O_technologies#...

Or Unix's mmap, which predates Vista by a couple decades. (It was designed around the time of 4.2BSD, i.e., 1983* .) I'd be shocked if Windows hasn't had a similar mechanism for years, as well.

* _The Design and Implementation of the 4.4BSD Operating System_, McKusick et al., p. 29-30.

Re: Computers are fast

#39

Post by thelabyrinth » Wed, Oct 13, 2010, 12:08 AM UTC

alecco wrote: post #31

jjcm wrote: post #29

Earlier quoted context omitted.

SSD's have become viable in terms of $/GB to justify them in a server room these days. I'd highly recommend moving to them (for your boot drive/VMs at least). It will make a world of difference. $400 may seem like a lot to spend for 160GB of storage, but knocking off two orders of magnitude off your seek time quickly becomes worth it when you're running four VMs off it at once.

Seagate Momentus XT hybrid is very cool. Probably the best bang for the buck at the moment. http://www.anandtech.com/show/3734/seagates-momentus-xt-revi...

If you haven't read a lot about SSDs, you should read the big Anandtech article: http://www.anandtech.com/show/2738 .

I didn't think SSDs were that important until I read this and was like, "Oh, I should get one." Which I haven't done yet -- soon, though. When AppleCare on my iMac expires.

Re: Computers are fast

#40

Post by alecco » Wed, Oct 13, 2010, 12:31 AM UTC

thelabyrinth wrote: post #39

alecco wrote: post #31

Earlier quoted context omitted.

Seagate Momentus XT hybrid is very cool. Probably the best bang for the buck at the moment. http://www.anandtech.com/show/3734/seagates-momentus-xt-revi...

If you haven't read a lot about SSDs, you should read the big Anandtech article: http://www.anandtech.com/show/2738 . I didn't think SSDs were that important until I read this and was like, "Oh, I should get one." Which I haven't done yet -- soon, though. When AppleCare on my iMac expires.

SSD (80GB, Intel) + hybrid (500GB, Seagate)