Messages in this thread | | | From | Andrew Lutomirski <> | Date | Mon, 30 May 2011 07:35:33 -0400 | Subject | Re: [PATCH v2 08/10] x86-64: Emulate vsyscalls |
| |
On Mon, May 30, 2011 at 6:59 AM, Ingo Molnar <mingo@elte.hu> wrote: > > * Andrew Lutomirski <luto@mit.edu> wrote: > >> >> I'd advocate waiting until glibc 2.14 comes out with this change: >> >> http://sourceware.org/git/?p=glibc.git;a=commit;h=a8509ca540427502bd955f35296ff7b727c7a8a1 >> >> I want to add a warning (ratelimited to an extremely low rate) in v3 >> whenever any of the vsyscalls get used telling users that their legacy >> code is suffering a performance impact, but it seems like bad form to >> tell people to build glibc from git to avoid a regression. > > But only statically built binaries would be impacted in practice, > right? The number of statically built binaries that heavily rely on > vsyscalls ought to be a very small set ...
With current glibc even dynamic binaries take the hit on time().
With the emulation warning (coming in v3), I get (on a Fedora 15-based VM):
[ 0.635493] init[1] emulated legacy vsyscall time(); upgrade your code to avoid a performance hit. ip:ffffffffff600404 sp:7fff277fe9c8 caller:3da3e9e27d in libc.so.6[3da3e00000+192000]
--Andy
| |