Re: 2.6.8-rc2-mm2

Hideo AOKI
2004-08-05T10:59:42Z

Hi,

Rik van Riel wrote:

> I would really appreciate any testing results on this, both good
> and bad. I want to get this thing tuned and into a generally good
> shape for use by everybody upstream.
>
> I'm especially interested in how this affects compute servers,
> desktops and heavily overloaded network servers (the "spamassassin
> slowed my system to a crawl" symptom would be one to test ;)).
>
> I suspect the patch may need some tweaking to help interactivity
> in some cases, but maybe it'll already work magically by itself...

To evaluate your patch, I tested -mm kernels for thrashing generated
by our benchmark suit.

In 2.6.8-rc2-mm2, performance of application increased, and overhead
of kernel decreased.

** Overview of workload

Benchmark program creates disk I/O processes and shared memory access
processes. Generating disk I/O and shared memory access at the same
time.

** Detailed environment of performance evaluation

- Hardware
CPU: Xeon 1.6GHz * 4
Memory: 2GB
HDD: IDE ATA100

- The benchmark suit
The benchmark suit is the wblg-disk, which I have released on
SourceForge.

<http://sourceforge.net/project/showfiles.php?group_id=110454&package_id=119281>
# I used alpha version (1.0.3-alpha) in this test.
# I will release 1.0.3 soon.

- configuration of benchmark
1. disk IO workload
+ number of process: 4 processes
+ read/write ratio: read 0% / write 100%
+ file IO size: 1KB - 256KB (random)

2. memory access workload
+ number of process: 32 processes
+ Shard memory regions: 512MB * 4
+ Each process accesses one shared memory region.
(8 processes share one shared memory region.)
+ Each process repeats 4 byte memory access each 4KB.

Measurement time: 1 hour
Measurement items: write throughput

- Other configurations
Using Oprofile
Issue vmstat command each 1 minute

** Results of performance evaluation

* result of benchmark
write throughput [MB/s]
2.6.8-rc2-mm1: 2.39
2.6.8-rc2-mm2: 2.68

* result of vmstat
swap in(kB/s) swap out(kB/s)
2.6.8-rc2-mm1: 0 - 641 0 - 583
2.6.8-rc2-mm2: 0 - 727 0 - 684

* results of Oprofile

- System profiling (top 2)

Overhead of kernel decreased by 3.9%.

2.6.8-rc2-mm1:
No. samples %
1. 170981153 77.6102 wblg-disk_client
2. 46808551 21.2469 vmlinux-2.6.8-rc2-mm1

2.6.8-rc2-mm2:
No. samples %
1. 179798682 81.6102 wblg-disk_client
2. 38141112 17.3122 vmlinux-2.6.8-rc2-mm2

- Kernel profiling (top 10)

Ratio of page_referenced_one() and kmap_atomic() decreased.

2.6.8-rc2-mm1:
No. samples % symbol name
1 11398599 24.3515 page_referenced_one
2 5652276 12.0753 kmap_atomic
3 2257662 4.8232 sysenter_past_esp
4 2098275 4.4827 flush_tlb_others
5 1467288 3.1347 __copy_to_user_ll
6 1167740 2.4947 page_address
7 1145108 2.4464 page_fault
8 946909 2.0229 flush_tlb_page
9 889151 1.8995 do_gettimeofday
10 828174 1.7693 refill_inactive_zone

2.6.8-rc2-mm2:
No. samples % symbol name
1 6057840 15.8827 page_referenced_one
2 3707571 9.7207 kmap_atomic
3 2531840 6.6381 sysenter_past_esp
4 1707017 4.4755 __copy_to_user_ll
5 1328610 3.4834 flush_tlb_others
6 1233726 3.2346 page_fault
7 1140917 2.9913 do_gettimeofday
8 970534 2.5446 get_offset_tsc
9 759579 1.9915 mark_offset_tsc
10 650208 1.7047 page_address

Best regards,
Hideo AOKI

Systems Development Laboratory, Hitachi, Ltd.