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Re: /tmp as tmpfs and consequence for imaging software

On Sun, Nov 13, 2011 at 9:50 AM, Josselin Mouette <joss@debian.org> wrote:
> Le dimanche 13 novembre 2011 à 09:40 +0100, Bastien ROUCARIES a écrit :
>> No it is not true. Science and imaging software are better to use true
>> disk baked file. For instance, if I want ot invert a big matrix they
>> are pretty good algorithm that force only some part of the file to be
>> keep on disk. They known better than kernel when to put somepart on
>> the data on the slow disk.
> The application might know better its usage profile, but the kernel
> knows better how the actual hardware behaves. This is why there are now
> some APIs to give hints to the kernel instead of assume the application
> can deal with everything by itself.
>> And do not ask user to choose. Imageging software and movie maker
>> software have the same requirement than high performance science
>> software.
> Having to deal with quite a lot of HPC software, I can assure you that
> most of such applications do not know how to use disk or memory
> correctly. They see considerable speedup when using tmpfs - as soon as
> you don’t use it for too large files, of course.

Yes it the problem file bigger than memory.

>> Now that are the solution ? We could not increase tmpfs over 50% to
>> 70% of physical ram without deadlock (OOM and so on). And it is not
>> enought for your use. Should we use /var/tmp  ? But it does not fit
>> due to "Files and directories located in /var/tmp must not be deleted
>> when the system is booted" (FHS). Whereas this kind of software want
>> to be non persistant and tru file backed.
>> Any suggestion is welcome
> In all cases, do not assume /tmp was ever made for such a use case. You
> need to locate your data somewhere else. Doing like gimp, which uses
> $HOME but allows the user to specify something else, is a good way to
> go.

Ok could we made some policy about /tmp use ? Like do not create file
above 10M ? And fill RC bug if the apps do this ?

$HOME is not really nice but it could work. I have a tmp dir under my
home directry and some script to clean up at every log on.

Could we agree to mass report bug on this issue?

> --
>  .''`.      Josselin Mouette
> : :' :
> `. `'
>  `-

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