Linux 2.4.19-pre5

rwhron
2002-03-30T18:48:25Z

> This release has -aa writeout scheduling changes, which should improve IO
> performance (and interactivity under heavy write loads).

> _Please_ test that extensively looking for any kind of problems
> (performance, interactivity, etc).

2.4.19-pre5 shows a lot of improvement in the tests
I run. dbench 128 throughput up over 50%

dbench 128 processes
2.4.19-pre4 8.4 ****************
2.4.19-pre5 13.2 **************************

Tiobench sequential writes:
10-20% more throughput and latency is lower.

Tiobench Sequential reads
Down 7-8%.

Andrew Morton's read_latency2 patch improves tiobench
sequential reads and writes by 10-35% in the tests I've
run. More importantly, read_latency2 drops max latency
with 32-128 tiobench threads from 300-600+ seconds
down to 2-8 seconds. (2.4.19-pre5 is still unfair
to some read requests when threads >= 32)

I'm happy with pre5 and hope more chunks of -aa show
up in pre6. Maybe Andrew will update read_latency2 for
inclusion in pre6. :) It helps tiobench seq writes too.
dbench goes down a little though.

Max latency is the metric that stands out as "needs
improvement" and "fix exists".

tiobench seq reads 128 threads
MB/s max latency
2.4.19-pre1aa1 6.98 661.3 seconds
2.4.19-pre1aa1rl 9.55 7.8 seconds

tiobench seq writes 32 threads
MB/s max latency
2.4.19-pre1aa1 15.46 26.1 seconds
2.4.19-pre1aa1rl 17.31 18.0 seconds

The read latency issue exists on a 4 way xeon
with 4GB ram too. Max latency jumps to 270 seconds
with 32 tiobench threads, and is over 500 seconds when
threads >= 128. (latency in milliseconds below)

Sequential Reads
Num Avg Maximum Lat% Lat%
Kernel Thr Rate (CPU%) Latency Latency >2s >10s
-------------- --- ------------------------------------------------------
2.4.19-pre5 1 38.46 23.94% 0.302 111.14 0.00000 0.00000
2.4.19-pre5 32 30.24 21.69% 9.883 270391.48 0.01106 0.00915
2.4.19-pre5 64 30.08 21.67% 17.868 357219.21 0.01965 0.01807
2.4.19-pre5 128 30.40 22.77% 30.460 520607.27 0.02714 0.02569
2.4.19-pre5 256 29.07 21.96% 56.444 539381.86 0.05378 0.05197

The behemoth benchmark page:
http://home.earthlink.net/~rwhron/kernel/k6-2-475.html

--
Randy Hron