[Qemu-devel] TCG slowdown

[Edgar E. Iglesias]

Lately, my TCG emulated machines have been running terribly slow.
Like a factor 3 or 4 slower, hardly usable.

I bisected it to this:

commit d5ab9713d2d4037fd56b0adddd26c8d4dc11cf09
Author: Jan Kiszka <address@hidden>
Date:   Tue Aug 2 16:10:21 2011 +0200

    Avoid allocating TCG resources in non-TCG mode
    
    Do not allocate TCG-only resources like the translation buffer when
    running over KVM or XEN. Saves a "few" bytes in the qemu address space
    and is also conceptually cleaner.
    
    Signed-off-by: Jan Kiszka <address@hidden>
    Signed-off-by: Anthony Liguori <address@hidden>


It turns out that the init of the tb cache is now moved to before ram_size
gets it's default value. And because the default tb cache size, if no
-tb-size option is given, is based on the ram_size it is now zero..

Cheers