2.4 vs 2.2 performance under load comparison

2.4 vs 2.2 performance under load comparison

[Lars Marowsky-Bree]

Good morning,

I did a comparison between 2.4 and 2.2.18 (+ Andrea's patches), using the
respective latest SuSE kernels, but the results should apply to the versions
in general.

Situation: SAP R/3 + SAP DB + benchmark driver running on a single node 4 CPU
SMP machine, tuned down to 1GB of RAM.

Running the SAP benchmark with 75 users on 2.2 yields for the first benchmark
run:

- 7018ms average response time
- 2967s CPU time in 1136s elapsed time
- ~500MB swap allocated
- ~1500 pages paged in/s, 268 pages/out/s on average

Running the same benchmark on 2.4:

- ~700ms average response time
- 1884s CPU time in 669s elapsed time
- ~500MB swap allocated
- ~50 pages paged in, ~212 pages paged out per second on average

Running the same benchmark the second time on both machines to get them warmed
up, 2.2 stays in approximately the same range, while 2.4 gets even _better_,
dropping down to ~350ms response time and ~20 pages in/out.

This is a rather amazing improvement in swapping performance.

Rik, it's time for you to break it again *g*

Sincerely,
    Lars Marowsky-Brée <lars.marowsky-bree@sap.com>
    SuSE Linux AG at the SAP LinuxLab - lmb@suse.de

-- 
Perfection is our goal, excellence will be tolerated. -- J. Yahl

Re: 2.4 vs 2.2 performance under load comparison

[Rik van Riel]

On Thu, 22 Feb 2001, Lars Marowsky-Bree wrote:

> Situation: SAP R/3 + SAP DB + benchmark driver running on a
> single node 4 CPU SMP machine, tuned down to 1GB of RAM.
>
> Running the SAP benchmark with 75 users on 2.2 yields for the
> first benchmark run:
>
> - 7018ms average response time
> - 2967s CPU time in 1136s elapsed time
> - ~500MB swap allocated
> - ~1500 pages paged in/s, 268 pages/out/s on average
>
> Running the same benchmark on 2.4:
>
> - ~700ms average response time
> - 1884s CPU time in 669s elapsed time
> - ~500MB swap allocated
> - ~50 pages paged in, ~212 pages paged out per second on average

> Rik, it's time for you to break it again *g*

Actually, in 2.4 we have one big VM balancing problem left.

We have no way to auto-balance between refill_inactive_scan()
and swap_out(), so we can (and probably do) still end up paging
out the wrong pages lots of times ... this is alleviated somewhat
by having a 1-second inactive list, but still...

Another problem is a lack of smarter IO clustering, when we get
that better I'm sure we can increase performance even more.

regards,

Rik
--
Virtual memory is like a game you can't win;
However, without VM there's truly nothing to lose...

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