Re: Learning

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"William" == William Lee Irwin <wli@holomorphy.com> writes:
William> Well, consider it briefly for a moment:
William> Q1: what takes the most time during boot?
William> A1: inefficient userspace initialization
William> 	but worse yet, firmware stuff

On Wed, Jan 23, 2002 at 11:10:04AM +0200, Momchil Velikov wrote:
> We don't (re)boot :)

Noble, but perhaps more worthy of a system administrator than a kernel
hacker given the old "You mess up, you reboot" rule, and the further
constraint that testing a new kernel patch requires rebooting...

"William" == William Lee Irwin <wli@holomorphy.com> writes:
William> Q2: what takes the most time during application startup?
William> A2: disk accesses
William> A1 and A2 have some impact on what could perhaps be considered
William> important (to some people) aspects of performance. For instance,
William> boot times contribute to some rather large latencies important
William> to clustering folk.

On Wed, Jan 23, 2002 at 11:10:04AM +0200, Momchil Velikov wrote:
>   "Using a cluster to hide the fact that the underlying systems crash
>   regularly is an extremely dangerous way to manage a computing
>   environment."
>                               -- Matt Dillon

In my heart of hearts I'm in general agreement with this notion.
I don't have any particular defense of the clustered computing model
offhand aside from the vague notion that with large enough collections
of hardware, hardware failure rates start to require full-time teams
of individuals dedicated to replacing failed disks nonstop 24/7...

"William" == William Lee Irwin <wli@holomorphy.com> writes:
William> At any rate, the filesystem profiling + defragmentation doesn't
William> seem like a bad idea at all, though I'm wondering how much of it could
William> be driven from userspace. Probably the minimal kernel support needed
William> would be some kind of inode-based access profiling. So (2) perhaps
William> also has an answer.

On Wed, Jan 23, 2002 at 11:10:04AM +0200, Momchil Velikov wrote:
> Defragmentation may result as a side effect of online logical volume
> resizing effort.

I think the sort of defragmentation sought here is specific to the
on-disk organization individual files determined by profiling to be
important, not block allocation in general.


Cheers,
Bill
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