2.5.44-mm1 with contest

Here are contest 0.51 benchmarks for 2.5.44-mm1 with shared pagetables enabled:

noload:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [2]          73.4    93      0       0       1.03
2.5.44 [3]              74.6    93      0       0       1.04
2.5.44-mm1 [3]          75.0    93      0       0       1.05

process_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [2]          105.8   71      44      31      1.48
2.5.44 [3]              90.9    76      32      26      1.27
2.5.44-mm1 [3]          191.5   36      168     64      2.68

These were all checked to ensure it was not one pathological run making the value high. The range was 190.6->192.7.

ctar_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [1]          92.3    82      1       5       1.29
2.5.44 [3]              97.7    80      1       6       1.37
2.5.44-mm1 [3]          99.2    78      1       6       1.39

xtar_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [2]          171.0   45      2       8       2.39
2.5.44 [3]              117.0   65      1       7       1.64
2.5.44-mm1 [3]          156.2   49      2       7       2.19

io_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [2]          301.1   26      21      11      4.22
2.5.44 [3]              873.8   9       69      12      12.24
2.5.44-mm1 [3]          347.3   22      35      15      4.86

read_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [1]          105.7   73      6       4       1.48
2.5.44 [3]              110.8   68      6       3       1.55
2.5.44-mm1 [3]          110.5   69      7       3       1.55

list_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [1]          98.9    72      1       23      1.39
2.5.44 [3]              99.1    71      1       21      1.39
2.5.44-mm1 [3]          96.5    74      1       22      1.35

mem_load:

Kernel [runs]           Time    CPU%    Loads   LCPU%   Ratio
2.5.43-mm2 [2]          106.5   69      27      2       1.49
2.5.44 [3]              114.3   67      30      2       1.60
2.5.44-mm1 [3]          159.7   47      38      2       2.24

Notably different results in many places. This is a similar pattern to the last time I enabled shared pagetables. I haven't had the time to try without it enabled yet.

Con

Not really sure what's going on here. I hope you don't have one of those CPUs which magically slows down when it gets hot.

I tried it:

2.4.19
make -j6 bzImage 408.52s user 27.74s system 369% cpu 1:58.19 total make -j6 bzImage 406.61s user 26.79s system 376% cpu 1:55.24 total

slightly faster on the second run, more stuff was in cache.

2.5.44-mm2ish
1st make -j6 bzImage 417.03s user 34.95s system 376% cpu 2:00.14 total 2nd make -j6 bzImage 414.78s user 33.08s system 375% cpu 1:59.17 total

bit slower. So let's set HZ to 100:

2.5.44-mm2ish HZ=100
make -j6 bzImage 406.67s user 32.17s system 370% cpu 1:58.33 total make -j6 bzImage 404.79s user 30.66s system 377% cpu 1:55.27 total

That'll be the pipe change I guess.

It's not shared pagetables. It's lots of other things though. Mainly the IO scheduler.

Almost all of your tests are testing reads competing with reads, and reads competing with writes. We fiddled with that pretty fundamentally. The -mm patches have fifo_batch at 16 rather than 32, which explains most of the above differences. That change will cause an overall reduction in throughput for these sorts of loads.