SLUB with queueing (V2) beats SLAB netperf TCP_RR

The following patchset cleans some pieces up and then equips SLUB with per cpu queues that work similar to SLABs queues. With that approach SLUB wins significantly in hackbench and improves also on tcp_rr.

Hackbench test script:

#!/bin/bash
uname -a
echo "./hackbench 100 process 200000"
./hackbench 100 process 200000
echo "./hackbench 100 process 20000"
./hackbench 100 process 20000
echo "./hackbench 100 process 20000"
./hackbench 100 process 20000
echo "./hackbench 100 process 20000"
./hackbench 100 process 20000
echo "./hackbench 10 process 20000"
./hackbench 10 process 20000
echo "./hackbench 10 process 20000"
./hackbench 10 process 20000
echo "./hackbench 10 process 20000"
./hackbench 10 process 20000
echo "./hackbench 1 process 20000"
./hackbench 1 process 20000
echo "./hackbench 1 process 20000"
./hackbench 1 process 20000
echo "./hackbench 1 process 20000"
./hackbench 1 process 20000

Dell Dual Quad Penryn on Linux 2.6.35-rc3
Time measurements: Smaller is better:

Procs NR SLAB SLUB SLUB+Queuing %
-------------------------------------------------------------
100 200000 2741.3 2764.7 2231.9 -18
100 20000 279.3 270.3 219.0 -27
100 20000 278.0 273.1 219.2 -26
100 20000 279.0 271.7 218.8 -27
10 20000 34.0 35.6 28.8 -18
10 20000 30.3 35.2 28.4 -6
10 20000 32.9 34.6 28.4 -15
1 20000 6.4 6.7 6.5 +1
1 20000 6.3 6.8 6.5 +3
1 20000 6.4 6.9 6.4 0

SLUB+Q also wins against SLAB in netperf:

Script:

#!/bin/bash

TIME=60 # seconds
HOSTNAME=localhost # netserver

NR_CPUS=$(grep ^processor /proc/cpuinfo | wc -l)
echo NR_CPUS=$NR_CPUS

run_netperf() {
for i in $(seq 1 $1); do
netperf -H $HOSTNAME -t TCP_RR -l $TIME &
done
}

ITERATIONS=0
while [ $ITERATIONS -lt 12 ]; do
RATE=0
ITERATIONS=$[$ITERATIONS + 1]
THREADS=$[$NR_CPUS * $ITERATIONS]
RESULTS=$(run_netperf $THREADS | grep -v '[a-zA-Z]' | awk '{ print $6 }')

for j in $RESULTS; do
RATE=$[$RATE + ${j/.*}]
done
echo threads=$THREADS rate=$RATE
done

Dell Dual Quad Penryn on Linux 2.6.35-rc4

Loop counts: Larger is better.

Threads SLAB SLUB+Q %
8 690869 714788 + 3.4
16 680295 711771 + 4.6
24 672677 703014 + 4.5
32 676780 703914 + 4.0
40 668458 699806 + 4.6
48 667017 698908 + 4.7
56 671227 696034 + 3.6
64 667956 696913 + 4.3
72 668332 694931 + 3.9
80 667073 695658 + 4.2
88 682866 697077 + 2.0
96 668089 694719 + 3.9

SLUB+Q is a merging of SLUB with some queuing concepts from SLAB and a new way of managing objects in the slabs using bitmaps. It uses a percpu queue so that free operations can be properly buffered and a bitmap for managing the free/allocated state in the slabs. It is slightly more inefficient than SLUB (due to the need to place large bitmaps --sized a few words--in some slab pages if there are more than BITS_PER_LONG objects in a slab) but in general does not increase space use too much.

The SLAB scheme of not touching the object during management is adopted. SLUB+Q can efficiently free and allocate cache cold objects without causing cache misses.

The queueing patches are likely still be a bit rough around corner cases and special features and need to see some more widespread testing.

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