[IDEA] Tweaks

[namtih]

I only have some limited basic Linux skills and knowledge. So I want to ask you what you think would make sense to implement in future releases:
http://blog.extremeshok.com/archives/1081

I've implemented the following tweaks yesterday and all seems running fine. But I don't have/know any tools to check if there is a real performance gain.
- Dropbear
- Remove tty + getty (3-6)
- Replace Bash with Dash shell
- Optimize mount (often recommended in other threads too)
- Disable IPv6
- Replace Deadline Scheduler with NOOP Scheduler (I found some articles about NOOP and it was always recommended for flash drives like SD cards)
- Remove DHCP

I've also did:
- remove Samba binaries
- sync && sync && echo 3 > /proc/sys/vm/drop_caches

While looking for a new ROM for my Android device, I've also saw many scripts which should optimize the general performance of the device. Many are editing read caches, swap behavior, TCP tweaks and so on. But these settings are to unknown for me to see if it really would help and what are the best settings for the Pi. Here is for example one script:
http://forum.xda-developers.com/showthread.php?p=17870162&postcount=1
or
http://forum.xda-developers.com/showthread.php?t=1904438
Some is Android specific, but many tweaks are just basic Linux.

[CurlyMo]

1) Dropbear was replaces by SSH so we have SFTP and WinSCP availability
2) Marginal performance gain, but could be possible because we only use 1 and 2
3) We depend to much on Bash
4) Can you provide us with theoretical and practical test results
5) The ipv6 isn't loaded by default so ipv6 support isn't active by default. Users can activate it by loading the module themselves
6) Awaiting real world test results
7) Not an option
8) Needed for some XBMC functionality
9) We already clear caches when using xbian-config, however, we also want to implement clearing the caches on boot.

Remember that Raspbian was already more optimized for the RPi then debian because it's e.g. already using tmpfs for certain mountpoints. I will react on the other two links later...

[namtih]

Regarding point 4: mount options

defaults,noatime,nodiratime

Code:

root@xbian:/etc/default# hdparm -tT /dev/mmcblk0p2
/dev/mmcblk0p2:
Timing cached reads:   330 MB in  2.01 seconds = 164.55 MB/sec
Timing buffered disk reads:  52 MB in  3.09 seconds =  16.83 MB/sec

defaults

Code:

root@xbian:~# hdparm -tT /dev/mmcblk0p2
/dev/mmcblk0p2:
Timing cached reads:   324 MB in  2.00 seconds = 161.66 MB/sec
Timing buffered disk reads:  52 MB in  3.03 seconds =  17.14 MB/sec

So no big gain.

---

Regarding point6: NOOP scheduler

General:
http://www.vincentkong.com/de/wiki/-/wiki/Main/Android+IO+Schedulers
http://en.wikipedia.org/wiki/Noop_scheduler

Bad result:
http://www.redhat.com/magazine/008jun05/features/schedulers/

Good result:
http://mynixworld.wordpress.com/2011/11/10/how-to-choose-the-right-kernel-io-scheduler/

So again, no clear result.
I will leave it for now, but perhaps will try Deadline later.

[CurlyMo]

Of course the scheduler is not something you can test by only looking at the throughput. The differences between HDDs and SD cards are also in the random read/write, access times, write cycles etc. So a more profound test is needed to actually draw conclusions.

[raspberry_pd]

Removing DHCP and BASH seem out of the question to me.

[namtih]

(27th Dec, 2012 12:03 AM)raspberry_pd Wrote:  Removing DHCP and BASH seem out of the question to me.

It wasn't meant to deactivate it in standard. I wanted to show some options which might be perhaps worth to add as optional services in the xbian-config tool.

[BartOtten]

Namtih: The advantages of those tweaks is nothing compared to tweaking the CPU/overclocking. That (and optimizing XBMC) is the real speed booster. I do like to make the system tweakable but I think we have more important tweaks XBian can work on. For example: install on USB, more packages to install from XBian-config, better remote support.

Big plus (reputation) for trying to help I really like that!

[BartOtten]

Maybe this can be something for the SDHC: http://bartsjerps.wordpress.com/2011/02/22/disk-alignment-linux/

[CurlyMo]

This is not something SD card users should be worried about. It is meant for users with large capacity hard drives that use the advanced format sector size of 4KB instead of 512b. This difference is sector size is linked to ZFS (maintained by Oracle), which this article already talks about.