Linux's "Ondemand" Governor Is No Longer Fit

[Ericg]

I don't know about you but I have a really hard time using up 4GB of RAM on linux (KDE desktop). I don't even use a swap. I could see if you edit a lot of RAW images, have large video projects open, or run virtual machines, you might run out, but 4GB seems plenty enough for me for a long time. On OS X (Mountain Lion) even after an upgrade from 4GB to 8GB I was still running out of memory with fewer apps open!

Htop says: 1496mb of RAM used, of 3277MB available
Arch x64, KDE 4.10.3, firefox open with 7 tabs (3 are active thanks to Unload-- https://addons.mozilla.org/en-US/fir...don/unloadtab/). I did just close a lot of tabs about 5minutes ago though so maybe its not de-allocated that memory yet. Firefox is using the most memory, followed by virtuso (Nepomuk). A big chunk of that is probably in use by zRAM-- https://wiki.archlinux.org/index.php...cache_.2F_Zram.

And I can hit memory-pressure on occasion, mostly during compiles (/tmp is tmpfs with 3G alloted because im on an SSD and I didnt want to wear it out), hence 4GB of swap, and zRam.

[duby229]

Being an AMD fanboy I must say they really need a new chipstet! For me the weakest point right know is how bad the memory controller is compared with Intel solution, in benchmarking they offer truly poor results! Also PCI express 3.0 should already be implemented! While ASUS already provides a motherboard with pci e 3.0 on the 990fx chipset is not really a native solution.

The memory controller is on the CPU, not the chipset, and the PCIe spec is already at 3.0.

[AnonymousCoward]

Htop says: 1496mb of RAM used, of 3277MB available
Arch x64, KDE 4.10.3, firefox open with 7 tabs (3 are active thanks to Unload-- https://addons.mozilla.org/en-US/fir...don/unloadtab/). I did just close a lot of tabs about 5minutes ago though so maybe its not de-allocated that memory yet. Firefox is using the most memory, followed by virtuso (Nepomuk). A big chunk of that is probably in use by zRAM-- https://wiki.archlinux.org/index.php...cache_.2F_Zram.

And I can hit memory-pressure on occasion, mostly during compiles (/tmp is tmpfs with 3G alloted because im on an SSD and I didnt want to wear it out), hence 4GB of swap, and zRam.

Are you subtracting cache/buffers from used memory?

[Ericg]

Are you subtracting cache/buffers from used memory?

I'm just reading off the number from htop at the top, so if it automatically pulls out cache & buffers-- then yes. As good with linux as I have gotten over the years...I have yet to figure out how exactly memory reporting works to get a "real" answer ><.

Whats a good utility that will print out either the ram minus the cache and buffers, or that will print them side by side so I know what to subtract from the readout?

[ChrisXY]

 $ free -m
             total       used       free     shared    buffers     cached
Mem:         32070      30045       2025          0        154      25945
-/+ buffers/cache:       3945      28125
Swap:            0          0          0

Some ~4 GB are buffers and some ~26 GB are cached files. I think (used - cached + free ~= actual free) and that buffers is stuff that needs to be written somewhere before it can be cleared?

[gens]

I'm just reading off the number from htop at the top, so if it automatically pulls out cache & buffers-- then yes. As good with linux as I have gotten over the years...I have yet to figure out how exactly memory reporting works to get a "real" answer ><.

Whats a good utility that will print out either the ram minus the cache and buffers, or that will print them side by side so I know what to subtract from the readout?

its a bit complicated to get the actual memory usage, as described here

http://www.halobates.de/memorywaste.pdf

i got 4gigs and no swap
computer starts struggling around 3.6 and freezes or kills a process around 3.7, as reported by htop

[Ericg]

 $ free -m
             total       used       free     shared    buffers     cached
Mem:         32070      30045       2025          0        154      25945
-/+ buffers/cache:       3945      28125
Swap:            0          0          0

Some ~4 GB are buffers and some ~26 GB are cached files. I think (used - cached + free ~= actual free) and that buffers is stuff that needs to be written somewhere before it can be cleared?

When I took this measure, htop was reporting about ~812mb of RAM used, of 3277 total, so it was saying about 2,465mb free.

[eric@eric-laptop ~]$ free -m
             total       used       free     shared    buffers     cached
Mem:          3277       1849       1428          0          0       1033
-/+ buffers/cache:        815       2462
Swap:         3906          0       3906

So used - cache + free equals actual free? 1849 - 1033 + 1428? 2,244-- about the same that htop was saying, actually a little less free.

This was fresh-booting to an Arch x64 KDE (4.10.3) desktop and playing around a little bit with Docky, moving items around and the likes. No other programs had been opened (other than htop obviously to check it) since it first booted up.


EDIT:

After being in firefox and posting this original post I double checked it just so we'd have a "before and after" snapshot. Htop is currently sitting at 1178mb used, of 3277. and free -m reports...

[eric@eric-laptop ~]$ free -m
             total       used       free     shared    buffers     cached
Mem:          3277       2324        953          0          0       1140
-/+ buffers/cache:       1183       2094
Swap:         3906          0       3906

EDIT 2: Btw, this was with ZRAM disabled, so nothing "extra" is purposefully sucking up RAM.

[halo9en]

So, what about those power/performance benchmarks, Michael?

[ChrisXY]

So used - cache + free equals actual free?

No, what I wrote is pretty much nonsense. I shouldn't be allowed to post late at night.

What I meant to say was: cached + free is about the free ram, because cached is that ram that can be free'd quickly when demand is there and it contains stuff like files/directory listings you had opened recently.

The issue is only that free displays ram as used when it really is "used", even by stuff that can be safely discarded.

[curaga]

That's why free displays the "-/+ buffers/cache" line. Those numbers are the "proper" used ones*.

* Except if you're making use of tmpfs, which is listed as cache, but cannot be freed on demand.