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Re: Env var to tunable mapping?
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: "Carlos O'Donell" <carlos at redhat dot com>
- Cc: "Paul E. Murphy" <murphyp at linux dot vnet dot ibm dot com>, Roland McGrath <roland at hack dot frob dot com>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, Tulio Magno Quites Machado Filho <tuliom at linux dot vnet dot ibm dot com>
- Date: Mon, 7 Sep 2015 12:30:32 +0530
- Subject: Re: Env var to tunable mapping?
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- References: <55D358D8 dot 7020303 at linux dot vnet dot ibm dot com> <55D3615F dot 1020300 at linaro dot org> <55D3AA72 dot 7000901 at linux dot vnet dot ibm dot com> <55D48F62 dot 6010902 at linaro dot org> <55D4ADC7 dot 3050008 at linux dot vnet dot ibm dot com> <20150819174147 dot GO2415 at spoyarek dot pnq dot redhat dot com> <55E732E1 dot 1070106 at redhat dot com>
On Wed, Sep 02, 2015 at 01:33:21PM -0400, Carlos O'Donell wrote:
> To be clear it was Roland McGrath who supported the position that we have
> a single env var for all tunables. I heard no other opinions for this case.
>
> I do not support that position. I posit we should have one tunable per env
> var, and that we should follow namespace rules for those env vars e.g.
> always start with GLIBC_*. There is precedent for this, the Gnome xdg-app
> framework is already exporting XDG_* env vars in a sensible namespace, and
> as a framework just above us, they already have to deal with this kind of
> pseudo-API.
I am still ambivalent about this. I don't see there being too many
tunables, so a single string should be fairly easy to parse and write.
That said, this is an advantage for the individual envvars too, since
we won't have too many environment variables to manage. The single
environment variable has an additional advantage; the tunable list can
be initialized very early and will likely be cheaper than having to
traverse the environment for each environment variable.
Siddhesh