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[Nicholas Leskiw <question191807@xxxxxxxxxxxxxxxxxxxxx>]

Question #191807 on Graphite changed:
https://answers.launchpad.net/graphite/+question/191807

    Status: Open => Answered

Nicholas Leskiw proposed the following answer:
You'll have to stress test that before we'd accept it into graphite.  I
have think nagging feeling that to address both the beginning and end of a
file you'll need to have enough memory to map the entire file, and
repeatedly mapping huge blocks of memory like that might not be a huge
speedup.

But if you can get some data to prove that it's considerably faster,
doesn't crash with out of memory issues, and it doesn't break my staging
environment we'll consider it...

-Nick

On Tue, Mar 27, 2012 at 1:20 AM, Amos Shapira <
question191807@xxxxxxxxxxxxxxxxxxxxx> wrote:

> Question #191807 on Graphite changed:
> https://answers.launchpad.net/graphite/+question/191807
>
> Description changed to:
> I read in one of the answers (comment #4 in
> https://answers.launchpad.net/graphite/+question/170794) that
> carbon-cache keeps writing to both the first and last blocks of each .wsp
> file.
> This means that it has to keep doing lseek+read+write system calls  every
> time it updates the file.
> I'm not very familiar with Python but a quick search tells me that it
> supports mmap (http://docs.python.org/library/mmap.html).
> Using mmap(2) could give a huge advantage:
> 1. No system calls (which are expensive).
> 2. No copying of data between the process user-space and kernel buffers on
> each read/write
>
> What do you say?
>
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