On Tue, 7 Nov 2006, Peter Gutmann wrote:

> "Saqib Ali" <[EMAIL PROTECTED]> writes:
> >I compile a lot of software on my laptop, and I *certainly notice* the
> >difference between my office laptop (no encryption) and my travel laptop
> >(with FDE). The laptops are exactly the same, with the same image loaded. The
> >only difference is the FDE software that is installed on the travel laptop.
> That's because you're doing something that produces worst-case
> behaviour.  The (obvious) solution is the standard "don't do that,
> then".  My main development machine builds to a RAM drive, and for
> some odd reason I don't notice any disk access latency at all.

I am not sure that compilation is worst case for disk performance:
once system compiled the first file, the compiler and most of .h files
are in RAM and should not be fetched from disk. Note that RAM of
modern computers is large enough to store all the source code of a
project (except, maybe, openoffice.org).

My guess is that slow compilation is a result of access time
misconfiguration: if a filesystem has access time enabled, then each
time a file is read, the file system updates access time on disk. A
solution is to set noatime option on the filesystem used for
compilation. A better approach is to mount tmpfs as /tmp, and build in
/tmp (for openoffice.org compilation increase size and number of
inodes with size and nr_inodes options).


P.S. Probably of interest for disk benchmarker: disk performance
depends on which cylinders are used, so if one has two partitions (one
near the center and another one near the outer edge of the disk)
performance on these partitions can be different.

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