Mailinglist Archive: opensuse (1470 mails)

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Re: [opensuse] Re: real world cache vs ram
On 02/14/2016 09:39 AM, Olav Reinert wrote:
The interesting property to test is caching, meaning we expect repeated
access of the same files to show increasing performance because the
cache hit rate increases.

Yes but is that reasonable? In the real world, I mean?

Suppose we have a web site and the server is taking $LARGENUM hits per
second. All manner of files will keep being accessed as well as the
one relating to pages being hit (it gets more complicated if this is a
dynamic site and pages come from databases), the dot-htacess, the cgi
code (perl, python, java, ruby, whatever), the static graphics file for
the eye--candy. Over and over and over, the same files.

It strikes me that this is a better test situation than a rigged test.
its the kind of thing which, if the caching mechanism works, is likely
to sell because it has demonstrable value.

But it also ha to compete with the systems own ability to cache open
files via the memory mapping and the page caching algorithms, and gets
back to the issue of is this better served by more RAM.

Somewhere, the capacity of the motherboard to support more RAM will run
out. That's where running a test like this becomes valid.


--
A: Yes.
> Q: Are you sure?
>> A: Because it reverses the logical flow of conversation.
>>> Q: Why is top posting frowned upon?

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