[Xen-devel] Re: Brief TLS/PAE/xenbus/AGP/Debian/VCS questions

[Nuutti Kotivuori <naked@xxxxxx>]

Rik Van Riel wrote:
> On Thu, 30 Jun 2005, Mark Williamson wrote:
>
>>> What's happending with the TLS issue? Is /lib/tls still harmful? 
>>> There was talk of a glibc patch - did that ever progress anywhere? 
>>> Did making it work require changes to Xen as well as glibc?
>>
>> Not harmful but slower.  There is a glibc patch, which you can
>> apply if you want (the nicest would be for a distro to ship it).
>> The glibc people weren't interested in merging it.
>
> I think the glibc people just created a new glibc variant,
> which is in Fedora Rawhide already.

I went digging around for the patch and eventually had to a Fedora
glibc source RPM package to find it - is it available in any sane
place?

Compiling with '-mno-tls-direct-seg-refs' is still needed as well I
guess.

So, just to clarify the loose ends.

Using TLS is now perfectly safe, only causes a performance loss? Glibc
is the biggest culprit in losing performance - how much is this in
practise?

Does the patch given fix most of the performance loss, or the compiler
flag given, or are both needed to avoid most of it?

Why would glibc not take it in the standard version, but only a
variant? Is this variant included in the standard glibc distribution
and can it be enabled by some compile option? I would assume there's a
slight performance degration because of it or something.

Are there any valid reasons for not including that in, say, the
default Debian glibc?

Thanks again, you've been very helpful, as always.

-- Naked



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