Hi Jens -

Two patches: 

1. Adds in the IRQ saving to generic_smp_call_function_single_interrupt (as you had suggested).
2. Ensures a single IPI generated to get a remote function call handler going. 

So far it is working better than before on the 4-way IA64 w/ the mkfs/untar/make test suite - after 22 runs:

Part  RQ   MIN     AVG     MAX      Dev
----- --  ------  ------  ------  ------
 mkfs  0  18.786  19.253  19.655   0.241
 mkfs  1  18.639  19.182  19.786   0.293

untar  0  17.140  17.486  18.250   0.322
untar  1  16.951  17.494  18.274   0.350

 make  0  22.927  24.310  34.339   2.287
 make  1  22.863  23.788  24.189   0.333

 comb  0  59.478  61.049  70.320   2.142
 comb  1  59.875  60.463  61.305   0.458

 psys  0   3.96%   4.14%   4.39%   0.100
 psys  1   3.60%   3.85%   4.19%   0.176

So we're seeing reduced time (~1.0%) and reduced %sys to do it (7.0%). The tighter deviations for make with rq=1 may be interesting... :-)

I've compiled & booted the patches for x86_64 - rq=1 is working on that platform too.

Alan

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