Superfetch

[spyordie007]

This topic's title should be changed to "prefetch"; the OP has nothing to do with "superfetch"...

 

[Phoenix86]

Originally posted by: bsobel

Originally posted by: Phoenix86
Well it's hokey, that's for sure. I guess it'd be faster that using the HDD, but still...

For systems that aren't memory bound, aka they have enough RAM to run all apps w/o paging, this wouldn't help. Most of us should have "enough" memory this shouldn't be a concern.

I don't understand this comment (from the articled link in the AT article) "and it works fantastic if you have boatloads of memory" I'd tend do disagree on face value and wonder how it helps these systems.

Looks to me (I skipped the PDC this year, I'll confirm when some of the folks get back) that they have an option to put the pre-fetch data onto flash memory (which should be faster than a hd). If you have alot of memory, they'll do even more prefetching (e.g. prior to you actually using the app, let the memory manager page it out if you don't).

In theory, it's not a bad idea. It's a further improvement to what prefetching already does.

Bill

RAM > USB > HDD. Why not just use RAM?

spyordie007, the source article says superfetch, not prefetch.
Text
The option is part of a technology called Superfetch designed to make the next version of Windows faster to use over time.

The AT article mentions both names.

 

[bsobel]

RAM > USB > HDD. Why not just use RAM?

I'm saying I believe the flash memory will be an alternate backing store for what is currently kept in your prefetch folder. You can't store it in RAM as it's volatile and pre-fetching comes into play the most when your first booting up. So, instead of storing this info on the HDD (where the head has to move to read it in addition to reading other non-prefetched data) why not store an additional copy in flash. Think of the flash as a cache for this one directory on your harddrive. If the flash isn't there, the system will just use the HD. If it is there, it's faster since the system can populate the page cache while the HDD is busy loading non-cached info.

Bill

 

[Phoenix86]

Originally posted by: bsobel

RAM > USB > HDD. Why not just use RAM?

I'm saying I believe the flash memory will be an alternate backing store for what is currently kept in your prefetch folder. You can't store it in RAM as it's volatile and pre-fetching comes into play the most when your first booting up. So, instead of storing this info on the HDD (where the head has to move to read it in addition to reading other non-prefetched data) why not store an additional copy in flash. Think of the flash as a cache for this one directory on your harddrive. If the flash isn't there, the system will just use the HD. If it is there, it's faster since the system can populate the page cache while the HDD is busy loading non-cached info.

Bill

Why not cache it to RAM instead? I know I'm missing something obvious here.

 

[bsobel]

Why not cache it to RAM instead? I know I'm missing something obvious here.

I've been responding quick so I probably wasn't clear. The purpose of prefetching is to pre-load the system cache (in RAM) with pages that a program is likely to need. This meta-data regarding the pages to cache (the pre-fetch data) has to be stored in non-volatile store like a harddrive or flash ram is its needed to exist across sessions (reboots). The end result is the data is cached in RAM, but the information about what to cache in RAM has to be stored in a more permanent form.

The first time you run a new app, the system memory manager creates the prefetch information about it. It then stores that on the harddrive so the next time (say the next day, after you've rebooted) you start that app it can check the pre-fetch information and use it if it's there. If you kept the pre-fetch info all in RAM, it would be lost when you powered down and you'd never get past the first profiling step to the step where you reuse the information.

That clear it up at all?
Bill

 

[spyordie007]

thanks for the info bill

 

[bsobel]

Originally posted by: spyordie007
thanks for the info bill

Don't take it at gospil, it's what I've infered from what I've seen about the feature. More info should start coming out as the PDC winds down today.

 

[Phoenix86]

Thanks for the info.

I'm still missing the improvement. I mean the data it's storing isn't the actual program data, it's just the meta-data of what to store. I mean my whole prefetch directory on my system is < 6MB. So I gain the benefit of accessing 6MB of meta-data this *hold index finger and thumb very closely together* much faster? Did I get that right?

I'll have to see the actual gains this provides, I'm skeptical to say the least.