On Thu, 2011-01-20 at 10:46 +0800, Andrew Morton wrote:

On Thu, 20 Jan 2011 10:34:18 +0800 Shaohua Li [off-list ref] wrote:

quoted

quoted

quoted

  Under a harddisk based netbook with Meego, the metadata readahead
reduced about 3.5s boot time in average from total 16s.

That's a respectable speedup.  And it *needs* to be a good speedup,
given how hacky all of this is!

But then..  reducing bootup time on a laptop/desktop/server by 3.5s
isn't exactly a world-shattering benefit, is it?  Is it worth all the
hacky code?

a laptop/desktop/server need read more data from hard disks, this will
give more bootup time saving I think, though not tested yet.

Well, the whole point of the patch is to improve boot times, so the
more boot-time testing you can do, the better that is!

each distribution uses its own readahead (data readahead) daemon, it's
time-cost to change the daemon, but I'll check if I get some data in a
desktop.

quoted

quoted

It would be much more valuable if those 3.5 seconds were available to
devices which really really care about bootup times, but very few of
those devices use rotating disks nowadays, I expect?

Currently most popular netbooks are using rotating disks actually. And
this will benefit laptop/desktop too.

But my point is that three seconds boot-time improvement for a system
which has an uptime of days or months isn't terribly exciting.

What *would* be terribly exciting is a three-second improvement for
cameras, cellphones, etc.  But they don't use spinning disks.

Can we expect *any* benefit for flash-type storage devices?  If so, how
much?

There should be no benefit for high end SSD, because they have high
throughput even for random IO. For low end flash-type storage devices,
this should have a little benefit, but won't expect much. I can't test a
camera or cellphone, I can test a USB disk in a desktop if you like.

Thanks,
Shaohua