SSD config: how to change default scheduler from cfq to deadline

[gsbsexzual]

I'm running pclos kde 2012 on my thinkpad w500.  I'm trying to optimize my system for use with the ssd linux is installed on.  I've configured swap and tmp, system alignment, and filesystem layer.  The only thing i can't figure out is how to change the scheduler to deadline on boot.  I can change it via the terminal while the system is running, but i want it to be persistent.  Can someone help me out?  I hope this is in the right place....

[rubentje1991]

Please check also if in /etc/fstab, that your SSD is configured with noatime instead of relatime (no access times written to disk when opening a file)...


Your question:
http://www.pclinuxos.com/forum/index.php?topic=89569.65

I'm using the vanilla 2.6.38.2 kernel.  I've been using the deadline scheduler.  I've read this is the right thing to use with an ssd.  I include elevator=deadline in my grub kernel options.

=> you have to change that in grub.conf to change it to a persistent check... (if I remember that correctly - can't find my post about it anymore - from about a year ago)....

[gsbsexzual]

UUID=d075a62b-7e6c-4d1e-ba26-8feb8df2bf70 / ext4 noatime,discard 1 1

that's part of my /ect/fstab  is there anything else i should include there?

and as far as changing the grub.conf, where do i find that?  i've done a search, and looked in the places where i thought it may be with no luck...

thanks for the help thus far and sorry for the noob questions

[rubentje1991]

Sorry, my mistake.....

Please look in /boot/grub/menu.lst
=> there you can make the appropiate changes 

[rubentje1991]

UUID=d075a62b-7e6c-4d1e-ba26-8feb8df2bf70 / ext4 noatime,discard 1 1

that's part of my /ect/fstab  is there anything else i should include there?

and as far as changing the grub.conf, where do i find that?  i've done a search, and looked in the places where i thought it may be with no luck...

thanks for the help thus far and sorry for the noob questions

Looks OK to me  (if I can remember it, that looks +/- the same as on my pc (with SSD))

[gsbsexzual]

ok thanks again.  here is the relevant line of menu.lst  :title linux
kernel (hd0,0)/boot/vmlinuz BOOT_IMAGE=linux root=UUID=d075a62b-7e6c-4d1e-ba26-8feb8df2bf70 quiet nokmsboot vmalloc=256M acpi=on vga=791
initrd (hd0,0)/boot/initrd.img

where do i go about adding the line elevator=deadline  ?

[gseaman]

Right after "vga=791" like this:

Code: [Select]

vga=791 elevator=deadline
Galen

[gsbsexzual]

awesome.  thanks.  i'll test it out

[gsbsexzual]

THANKS GUYS!  rebooted and it's now default.  love pclos and love this forum and the support.  i don't feel like making another thread, but will if anyone suggests i do.  but i'm also having a problem where my system can only access 3gb of ram although i have 4gb installed and soon plan to upgrade to 8gb.  i could have sworn i had read somewhere that as of a fairly current kernel, i should be able to access at least the 4gb.  i also read somewhere about updating the kernel to an i686 pae to gain access to above 3gb of ram?  I guess i'm a little bit confused.  what should i be doing to be able to access 4/8gb of ram?

[rubentje1991]

Open Synaptic, search for kernel....

Install a "kernel-x.x.xx.x-pclosx.pae" kernel (I'd even suggest the .pae.bfs)
=> don't remove other kernels, it doesn't hurt to have more than one installed

Thus, install, then reboot, and select the new kernel to boot in the GRUB menu... please have some minutes patience (that new kernel will initialize some things for the first time)
If such a new kernel doesn't work, reboot in the "old" one, and test another   (you may remove that not-working one then of course / report it here)...
=> normally, they all work well

But remember to change the /boot/grub/menu.lst again for that kernel (I don't think the adjusted settings are auto copied over - if it's the case, that's perfect of course  ) (for your deadline-scheduler)

[kaptain_zero]

Sorry, I came in the back door on this topic, but I've recently installed a couple of SSDs in my system and now use them as default boot disks.  As I understood it, current Linux kernels were SSD aware and no further efforts on my part were required?!?!? I can't fault the throughput on these disks.... 

I use a 128G SSD as / as well as /home, and added a 500G conventional disk mounted as /home/username/Desktop/Storage. I have a second set of disks, set up the same way, and simply clone to them on a weekly basis to serve as a backup.

If adding stuff to Grub is required, I'll be happy to do it.... but I wasn't aware it was required, and everything seems to be running fine?!?!?


Regards

Christian

[gsbsexzual]

it's just to further enhance the performance of the ssd, as to my understanding

[gsbsexzual]

downloading and going to try the new kernel soon and report back.  i'm going with the .pae.bfs one.  should i switch to bfs as my default scheduler?  or is deadline more where i want to be?  i've just read up on bfs and theoretically it seems nice, but it sounds like in practice is doesn't work as good as deadline does?   

[rubentje1991]

downloading and going to try the new kernel soon and report back.  i'm going with the .pae.bfs one.  should i switch to bfs as my default scheduler?  or is deadline more where i want to be?  i've just read up on bfs and theoretically it seems nice, but it sounds like in practice is doesn't work as good as deadline does?   

No, for SSD, deadline is the right scheduler in my opinion....
BFS in  .pae.bfs is not a disk scheduler, but a series of patches to adjust the kernel to perform better (by Con Kolivas)... In PCLinuxOS, we recommend it for use (it's also the stock choice)... but you may choose yourself of course (BFS is a task scheduler, an alternative to CFQ - what's standard delivered with the Linux kernel)

[kaptain_zero]

what should i be doing to be able to access 4/8gb of ram?

Install the following kernel: 3.2.18-pclos1.pae.bfs

pae kernals can access above 3.xG of ram... (I think up to 16G but don't quote me on that). It works here as I have 4 1G sticks and Gkrellm reports 4049M total memory.

Regards

Christian