[Xen-devel] Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

H. Peter Anvin wrote:
> Right now a number of the call sites contain a huge push/pop sequence 
> followed by an indirect call.  We can patch in the native code to 
> avoid the branch overhead, but the register constraints and icache 
> footprint is unchanged.
That's true for the pvops hooks emitted in the .S files, but not so true 
for ones in C code (well, there are no explicit push/pops, but the 
presence of the call may cause the compiler to generate them).
The .S hooks can definitely be cleaned up, but I don't think that's 
germane to Nick's observations that the mm code is showing slowdowns.
   J

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