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Re: Prelink hates me



Arjan van de Ven wrote:
ok so there are 2 rational sides to this that aren't a bug:
1) prelink will read in a lot of files into the filesystem cache, since
it'll have to know detailed information about a lot of libraries to do
it's job, only way to get that is to read them in.

The memory is not spent in the cache. It is as though it was used by programs, but top and ps show no programs using that much memory.


2) normally, when 5 running binaries use the same library, there is only
one copy of that library in memory. However, when a library gets
prelinked, a *new copy* of that library is put on disk (one with all the
prelink information), and new binaries that start and use that library
won't and cannot share it with the existing running binaries, so this
leads to temporarily increased real memory usage (temporary because
eventually all apps that use keep the old libs "in use" exit and only
"new library" applications are running). The exception can be very long
running applications (like cron.weekly) which now have library stuff
that is hardly ever used and the VM subsystem may choose to swap some of
that out.

This is also not the problem, since this happens on a laptop with frequent reboots.


Now I'm not saying that what you see is exclusively one of these, nor am
I saying there's no bug, but at least the cache subsystem showing lots
of ram is expected (and it should be given up mostly when it's needed).

The cache size shown by free is small, but all the memory is used. So it seems like the memory is used by programs. But top and ps show no programs that big.


Also, if the cache was big, almost no disk reading should happen when starting programs. But the contrary happens: the disk starts trashing, as if all the memory was used by some program, which seems to be the case according to the totals, but does not seem to be the case when you look at per-program memory usage.

--
Simon Perreault <nomis80 nomis80 org> -- http://nomis80.org



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