Re: Debian's 32-bit glibc vs AT_SYSINFO
On 2015-09-24 14:19, Andy Lutomirski wrote:
> Hi-
>
> It looks like 32-bit x86 Debian glibc doesn't use AT_SYSINFO. This
> kills syscall performance. Upstream glibc as well as Fedora's glibc
> work fine.
>
> This test:
>
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_compat&id=9d742073d4c0449b262dbe0a3dab4a7c1d831500
>
> inadvertently found this issue.
>
> Any ideas? I'm only barely a Debian user -- I have a Debian-based test VM.
By default, the 32-bit glibc on Debian is built for i586, which does not
have the sysenter/syscall instructions. Therefore it doesn't use
AT_SYSINFO.
Now you can install the libc6-i686 package, which as it's name says is
built for i686, and thus can use the sysenter/syscall instructions and
AT_SYSINFO. Then your test passes successfully.
Aurelien
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://www.aurel32.net
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