Re: [Qemu-devel] [PATCH] TCG: Improve tb_phys_hash_func()

[Aurelien Jarno]

On Fri, Dec 31, 2010 at 08:46:02PM +0100, Aurelien Jarno wrote:
> On Thu, Dec 30, 2010 at 05:55:38PM +0000, Blue Swirl wrote:
> > On Wed, Dec 29, 2010 at 9:27 PM, Aurelien Jarno <address@hidden> wrote:
> > > Most of emulated CPU have instructions aligned on 16 or 32 bits, while
> > > on others GCC tries to align the target jump location. This means that
> > > 1/2 or 3/4 of tb_phys_hash entries are never used.
> > >
> > > Update the hash function tb_phys_hash_func() to ignore the two lowest
> > > bits of the address. This brings a 6% speed-up when booting a MIPS
> > > image.
> > 
> > Nice! The beginning of functions may be aligned to 16 bytes. Would it
> > change the performance figures if one or two more bits were ignored?
> > 
> 
> It makes a noticeable difference on how the TBs are dispatched in the
> hash table, but only by a few percents (slightly more on ppc). I am not

Here I meant how TBs are dispatched after my patch has been applied.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net