Windows Superfech on SSD

lx07 said:

Why?

Prefetch loads often used pages into RAM which is faster (by far) than SSD. You can argue with the algorithm used but not the speed. I write software for banks and in the past I forced the currency rate table into RAM as I knew it was used a lot and didn't want it paged in from disk. These days I do not bother as it is done automatically by the OS as the OS keeps track of frequently used tables.

If you can find any empirical evidence at all that supports turning off superfetch/prefetch I'm all ears. Unfortunately you won't as it doesn't exist or either (a) we would all do it or (b) MS would do it.

Surely you must admit MS engineers are aware of the concept of SSDs - it is not as if the year is 2001 or anything.

If you can't supply any evidence then playing with services is clearly just another pointless outdated tinkering with the OS that adds complexity for no proven value.

As it can't fit all necessary data in RAM only it also writes to disk and read from it to make educated guess what might be needed next. When you start a program, it looks at only what's absolutely necessary to start it and so accelerates opening it.
It's easy to check if and how much it helps, start (open) a program, close it and start it again. If it starts faster it would mean that prefetch is doing it's job.

Hi,

It's easy to check if and how much it helps, start (open) a program, close it and start it again. If it starts faster it would mean that prefetch is doing it's job.

It will start faster regardless of whether "Prefetch" is enabled or not.

The underlying idea is also to avoid unnecessary I/O trafic and to reduce the number of unnecessary writes on an SSD.
With the vastly increased TBW on last gen SSDs this point may well be moot but still, I can't seem to measure any loss of speed with such services as prefetch, etc. disabled.

With plenty of a DRAM present there are far more effective softwares around than the ones offered by MS.

Cheers,

lx07 said:

I did do that Mike, I used this application PassMark AppTimer - Measure application startup time when I was trying to guesstimate what compression would be fastest on my system. (xpress8k was best for me with fast SSD and mediocre CPU, xpress16K was better with a slower disk).

The point is that in almost all cases the OS is going to have a better idea what to do with memory management than you or I. Probably. Better than me anyway.

Sure you can randomly turn off services and it might make an improvement. If however turning off Prefetch would always (or even often) be more efficient with SSD then I honestly don't think MS would leave it. What for? They can't be so incompetent as to be unaware of SSDs and certainly wouldn't leave it on to deliberately cripple the OS.

The idea is silly if you ask me.

It was doing it's job before, specially on slow HDDs, I know, I did that test long time ago. Problems were that there was much less RAM available and disks were smaller and except just accelerating program start it was also taking resources to run those programs. That's why it was sometimes beneficial to turn it off. It was just give and take and you had to choose what to do and what's more important. With SSDs, them being much faster it may not have that much of influence but resources are plentiful nowadays so even if it helps a little bit for starting programs, there's no really big change in further system performance.
There was a panic with early SSDs to limit writing to it as much as possible but prefetch doesn't really write much on disk, once you started all programs at least once, very,very little wring was done to disk.