On Thu, 19 Jan 2006, Joel Schopp wrote:
> > Benchmark comparison between -mm+NoOOM tree and with the new zones
>
> I know you had also previously posted a very simplified version of your real
> fragmentation avoidance patches. I was curious if you could repost those with
> the other benchmarks for a 3 way comparison. The simplified version got rid
> of a lot of the complexity people were complaining about and in my mind still
> seems like preferable direction.
>
To satisfy this request, I did a quick rebase of the list-based approach
against 2.6.16-rc1-mm1 to have a comparable set of benchmarks. I will post
the patches in the morning after a re-read.
The results here are in three sets
Set 1: -mm3 Vs list-based anti-frag
Set 2: -mm3 Vs zone-based anti-frag
Set 3: list-based anti-frag Vs zone-based anti-frag
In the headers, list-based is called mbuddy-v22. Zone based is called
zbuddy-v3 (versions 1 and 2 were only posted to lhms-devel)
>>> BEGIN SET 1: -clean Vs mbuddy-v22 <<<
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-mbuddy-v22
Time taken to extract kernel: 14 15
Time taken to build kernel: 741 741
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-mbuddy-v22
1 creat-clo 12273.11 12239.80 -33.31 -0.27% File Creations and Closes/second
2 page_test 131762.75 134311.90 2549.15 1.93% System Allocations & Pages/second
3 brk_test 586206.90 597167.14 10960.24 1.87% System Memory Allocations/second
4 jmp_test 4375520.75 4373004.50 -2516.25 -0.06% Non-local gotos/second
5 signal_test 79436.76 77307.56 -2129.20 -2.68% Signal Traps/second
6 exec_test 62.90 62.93 0.03 0.05% Program Loads/second
7 fork_test 1211.92 1218.13 6.21 0.51% Task Creations/second
8 link_test 4332.30 4324.56 -7.74 -0.18% Link/Unlink Pairs/second
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-mbuddy-v22
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 60 86
Failed allocs 215 189
DMA zone allocs 1 1
Normal zone allocs 5 0
HighMem zone allocs 54 85
EasyRclm zone allocs 0 0
% Success 21 31
HighAlloc Under Load Test Results Pass 2
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-mbuddy-v22
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 101 103
Failed allocs 174 172
DMA zone allocs 1 1
Normal zone allocs 5 0
HighMem zone allocs 95 102
EasyRclm zone allocs 0 0
% Success 36 37
HighAlloc Test Results while Rested
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-mbuddy-v22
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 141 242
Failed allocs 134 33
DMA zone allocs 1 1
Normal zone allocs 16 83
HighMem zone allocs 124 158
EasyRclm zone allocs 0 0
% Success 51 88
>>> END SET 1: -clean Vs mbuddy-v22 <<<
>>> BEGIN SET 2: -clean Vs zbuddy-v3 <<<
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-zbuddy-v3
Time taken to extract kernel: 14 14
Time taken to build kernel: 741 738
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-zbuddy-v3
1 creat-clo 12273.11 12235.72 -37.39 -0.30% File Creations and Closes/second
2 page_test 131762.75 132946.18 1183.43 0.90% System Allocations & Pages/second
3 brk_test 586206.90 603298.90 17092.00 2.92% System Memory Allocations/second
4 jmp_test 4375520.75 4376557.81 1037.06 0.02% Non-local gotos/second
5 signal_test 79436.76 81086.49 1649.73 2.08% Signal Traps/second
6 exec_test 62.90 62.81 -0.09 -0.14% Program Loads/second
7 fork_test 1211.92 1212.52 0.60 0.05% Task Creations/second
8 link_test 4332.30 4346.60 14.30 0.33% Link/Unlink Pairs/second
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 60 106
Failed allocs 215 169
DMA zone allocs 1 1
Normal zone allocs 5 8
HighMem zone allocs 54 0
EasyRclm zone allocs 0 97
% Success 21 38
HighAlloc Under Load Test Results Pass 2
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 101 154
Failed allocs 174 121
DMA zone allocs 1 1
Normal zone allocs 5 8
HighMem zone allocs 95 0
EasyRclm zone allocs 0 145
% Success 36 56
HighAlloc Test Results while Rested
2.6.16-rc1-mm1-clean 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 141 212
Failed allocs 134 63
DMA zone allocs 1 1
Normal zone allocs 16 8
HighMem zone allocs 124 0
EasyRclm zone allocs 0 203
% Success 51 77
>>> BEGIN SET 2: -clean Vs zbuddy-v3 <<<
>>> BEGIN SET 3: -mbuddy-v22 Vs zbuddy-v3 <<<
2.6.16-rc1-mm1-mbuddy-v22 2.6.16-rc1-mm1-zbuddy-v3
Time taken to extract kernel: 15 14
Time taken to build kernel: 741 738
2.6.16-rc1-mm1-mbuddy-v22 2.6.16-rc1-mm1-zbuddy-v3
1 creat-clo 12239.80 12235.72 -4.08 -0.03% File Creations and Closes/second
2 page_test 134311.90 132946.18 -1365.72 -1.02% System Allocations & Pages/second
3 brk_test 597167.14 603298.90 6131.76 1.03% System Memory Allocations/second
4 jmp_test 4373004.50 4376557.81 3553.31 0.08% Non-local gotos/second
5 signal_test 77307.56 81086.49 3778.93 4.89% Signal Traps/second
6 exec_test 62.93 62.81 -0.12 -0.19% Program Loads/second
7 fork_test 1218.13 1212.52 -5.61 -0.46% Task Creations/second
8 link_test 4324.56 4346.60 22.04 0.51% Link/Unlink Pairs/second
2.6.16-rc1-mm1-mbuddy-v22 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 86 106
Failed allocs 189 169
DMA zone allocs 1 1
Normal zone allocs 0 8
HighMem zone allocs 85 0
EasyRclm zone allocs 0 97
% Success 31 38
HighAlloc Under Load Test Results Pass 2
2.6.16-rc1-mm1-mbuddy-v22 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 103 154
Failed allocs 172 121
DMA zone allocs 1 1
Normal zone allocs 0 8
HighMem zone allocs 102 0
EasyRclm zone allocs 0 145
% Success 37 56
HighAlloc Test Results while Rested
2.6.16-rc1-mm1-mbuddy-v22 2.6.16-rc1-mm1-zbuddy-v3
Order 10 10
Allocation type HighMem HighMem
Attempted allocations 275 275
Success allocs 242 212
Failed allocs 33 63
DMA zone allocs 1 1
Normal zone allocs 83 8
HighMem zone allocs 158 0
EasyRclm zone allocs 0 203
% Success 88 77
>>> END SET 3: -mbuddy-v22 Vs zbuddy-v3 <<<
So, in terms of performance on this set of tests, both approachs perform
roughly the same as the stock kernel in terms of absolute performance. In
terms of high-order allocations, zone-based appears to do better under
load. However, if you look at the zones that are used, you will see that
zone-based appears to do as well as list-based *only* because it has the
EASYRCLM zone to play with. list-based was way better at keeping the
normal zone defragmented as well as highmem which is especially obvious
when tested at rest. list-based was able to allocate 83 huge pages from
ZONE_NORMAL at rest while zone-based only managed 8.
Secondly, zone-based requires careful configuration to be successful. If
booted with kernelcore=896MB for example, it only performs slightly better
than the standard kernel. If booted with kernelcore=1024MB, it tends to
perform slightly worse (more zone fallbacks I guess) and still only
manages slighly better satisfaction of high order pages.
On the flip side, zone-based code changes are easier to understand than
the list-based ones (at least in terms of volume of code changes). The
zone-based gives guarantees on what will happen in the future while
list-based is best-effort.
In terms of fragmentation, I still think that list-based is better overall
without configuration. The results above also represent the best possible
configuration with zone-based versus no configuration at all against
list-based. In an environment with changing workloads a constant reality,
I bet that list-based would win overall.
> Zone based approaches are runtime inflexible and require boot time tuning by
> the sysadmin. There are lots of workloads that "reasonable" defaults for a
> zone based approach would cause the system to regress terribly.
>
> -Joel
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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