Re: IO degradation in 2.4.17-pre2 vs. 2.4.16

Marcelo Tosatti
2001-12-04T02:55:58Z

Jason,

Yes, throughtput-only tests will have their numbers degradated with the
change applied on 2.4.16-pre2.

The whole thing is just about tradeoffs: Interactivity vs throughtput.

I'm not going to destroy interactivity for end users to get beatiful
dbench numbers.

And about your clients: Don't you think they want some kind of
decent latency on their side?

Anyway, thanks for your report!

On Sat, 1 Dec 2001, Jason Holmes wrote:

> I saw in a previous thread that the interactivity improvements in
> 2.4.17-pre2 had some adverse effect on IO throughput and since I was
> already evaluating 2.4.16 for a somewhat large fileserving project, I
> threw 2.4.17-pre2 on to see what has changed. Throughput while serving
> a large number of clients is important to me, so my tests have included
> using dbench to try to see how things scale as clients increase.
>
> 2.4.16:
>
> Throughput 116.098 MB/sec (NB=145.123 MB/sec 1160.98 MBit/sec) 1 procs
> Throughput 206.604 MB/sec (NB=258.255 MB/sec 2066.04 MBit/sec) 2 procs
> Throughput 210.364 MB/sec (NB=262.955 MB/sec 2103.64 MBit/sec) 4 procs
> Throughput 213.397 MB/sec (NB=266.747 MB/sec 2133.97 MBit/sec) 8 procs
> Throughput 210.989 MB/sec (NB=263.736 MB/sec 2109.89 MBit/sec) 16
> procs
> Throughput 138.713 MB/sec (NB=173.391 MB/sec 1387.13 MBit/sec) 32
> procs
> Throughput 117.729 MB/sec (NB=147.162 MB/sec 1177.29 MBit/sec) 64
> procs
> Throughput 66.7354 MB/sec (NB=83.4193 MB/sec 667.354 MBit/sec) 128
> procs
>
> 2.4.17-pre2:
>
> Throughput 96.2302 MB/sec (NB=120.288 MB/sec 962.302 MBit/sec) 1 procs
> Throughput 226.679 MB/sec (NB=283.349 MB/sec 2266.79 MBit/sec) 2 procs
> Throughput 223.955 MB/sec (NB=279.944 MB/sec 2239.55 MBit/sec) 4 procs
> Throughput 224.533 MB/sec (NB=280.666 MB/sec 2245.33 MBit/sec) 8 procs
> Throughput 153.672 MB/sec (NB=192.09 MB/sec 1536.72 MBit/sec) 16 procs
> Throughput 91.3464 MB/sec (NB=114.183 MB/sec 913.464 MBit/sec) 32
> procs
> Throughput 64.876 MB/sec (NB=81.095 MB/sec 648.76 MBit/sec) 64 procs
> Throughput 54.9774 MB/sec (NB=68.7217 MB/sec 549.774 MBit/sec) 128
> procs
>
> Throughput 136.522 MB/sec (NB=170.652 MB/sec 1365.22 MBit/sec) 1 procs
> Throughput 223.682 MB/sec (NB=279.603 MB/sec 2236.82 MBit/sec) 2 procs
> Throughput 222.806 MB/sec (NB=278.507 MB/sec 2228.06 MBit/sec) 4 procs
> Throughput 224.427 MB/sec (NB=280.534 MB/sec 2244.27 MBit/sec) 8 procs
> Throughput 152.286 MB/sec (NB=190.358 MB/sec 1522.86 MBit/sec) 16
> procs
> Throughput 92.044 MB/sec (NB=115.055 MB/sec 920.44 MBit/sec) 32 procs
> Throughput 78.0881 MB/sec (NB=97.6101 MB/sec 780.881 MBit/sec) 64
> procs
> Throughput 66.1573 MB/sec (NB=82.6966 MB/sec 661.573 MBit/sec) 128
> procs
>
> Throughput 117.95 MB/sec (NB=147.438 MB/sec 1179.5 MBit/sec) 1 procs
> Throughput 212.469 MB/sec (NB=265.586 MB/sec 2124.69 MBit/sec) 2 procs
> Throughput 214.763 MB/sec (NB=268.453 MB/sec 2147.63 MBit/sec) 4 procs
> Throughput 214.007 MB/sec (NB=267.509 MB/sec 2140.07 MBit/sec) 8 procs
> Throughput 96.6572 MB/sec (NB=120.821 MB/sec 966.572 MBit/sec) 16
> procs
> Throughput 48.1342 MB/sec (NB=60.1677 MB/sec 481.342 MBit/sec) 32
> procs
> Throughput 71.3444 MB/sec (NB=89.1806 MB/sec 713.444 MBit/sec) 64
> procs
> Throughput 59.258 MB/sec (NB=74.0724 MB/sec 592.58 MBit/sec) 128 procs
>
> I have included three runs for 2.4.17-pre2 to show how inconsistent its
> results are; 2.4.16 didn't have this problem to this extent. bonnie++
> numbers seem largely unchanged between kernels, coming in around:
>
> ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> 2512M 14348 81 49495 26 24438 16 16040 96 55006 15 373.7 1
> ------Sequential Create------ --------Random Create--------
> -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
> files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
> 16 3087 99 +++++ +++ +++++ +++ 3175 100 +++++ +++ 11042 100
>
> The test machine is an IBM 342 with 2 1.26 GHz P3 processors and 1.25 GB
> of RAM. The above numbers were generated off of 1 10K RPM SCSI disk
> hanging off of an Adaptec aix7899 controller.
>
> --
> Jason Holmes
> -
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