fs cache

[Daniel Bond]

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Vlad GURDIGA wrote:
> Hello,
> 
> I have FreeBSD 7-CURRENT and Ubuntu on the same computer but Firefox
> takes twice as long to start on a fresh boot. I've run some simple
> tests:
> - on FreeBSD it takes about 7 seconds on the first start and about 3
> on subsequent startups;
> - on Ubuntu it takes about 3 seconds on the first start and about 1 on
> subsequent startups;
> 
> The only difference I can see is that on Ubuntu, after first start of
> Firefox the memory use for cache is 22% vs. 0% on FreeBSD. My guess is
> that this is the cause of slower startups on FreeBSD.
> 
> My question is: can I tune UFS2 in such a way that the most frequently
> used desktop applications would remain for a longer time in disk
> cache?
> 
> In both cases I use GNOME 2.18, GNOME System Monitor 2.18, and Firefox 2.
> Both FreeBSD 7-CURRENT (src and ports tree) and Ubuntu 7.01
> (2.6.20-16-generic kernel) are up to date. Both are SMP and 32bit.
> Here is the system configuration:
> - Intel DP965LT mother-board;
> - dual-core Pentium D 820;
> - 1GB of dual-channel-enabled DDR2 PC5300 at 667 MHz;
> - Seagate, BARRACUDA 7200.7 Plus, 160GB, ST3160827AS, 8M cache, with NCQ;
> _______________________________________________
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Hi,

I would think it loads faster in linux due to a linux-feature called
prelink.

Most common applications make use of shared libraries. These shared
libraries need to be loaded into memory at runtime and the various
symbol references need to be resolved. For most small programs this
dynamic linking is very quick. But for programs written in C++ and that
have many library dependencies, the dynamic linking can take a fair
amount of time.

Prelinking does this in advance of starting the program, but it requires
that user runs "prelink" every time libraries are updated.

I think it is the effect of prelinking you are noticing here, ubuntu has
it on by default as far as I know, and I guess that the package-manager
does the prelinking for the user.

- -CURRENT also has some extra debugging in kernel that slows things down.

- -DB.
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