Mailinglist Archive: opensuse (4288 mails)
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Re: [opensuse] 10.3 and swap question on 4-GB ram
- From: Teruel de Campo MD <chusty@xxxxxxxxxxxxx>
- Date: Mon, 29 Oct 2007 22:28:51 -0600
- Message-id: <1193718531.19397.29.camel@xxxxxxxx>
On Mon, 2007-10-29 at 19:55 +0100, Carlos E. R. wrote:
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The Monday 2007-10-29 at 23:49 +0800, Chee How Chua wrote:
In /etc/fstab, you would do something like this, assuming you have two
drives on your machine.
/dev/sda1 swap swap pri=1 0.0
/dev/sdb1 swap swap pri=1 0.0
So how would you make SUSE use the swap space for suspend if the size
of both swap partitions adds up to the size of RAM?
If there were only 1 swap partition, the kernel would know from the
GRUB menu entry:
kernel /vmlinuz root=/dev/hdd6 vga=0x317 resume=/dev/sda1 splash=verbose
Will it work to have two resume sections like this:
kernel /vmlinuz root=/dev/hdd6 vga=0x317 resume=/dev/sda1
Now, this is an interesting question.
I have that situation, but my "resume=" entries only lists one of the two
swap partitions. It certainly works, but I can't say if the hibernation
data is stored on both drives o a single one, I don't know how to
determine that (any one of my swaps is bigger than my ram).
My guess is that hibernating occurs in two stages. First, tasks are
stopped and swapped out. At this time, the kernel is fully running, so it
uses both swaps. Later, it takes a "photo" of the remaining used ram and
this is copied to swap - and this might be only one of them.
However... a year or two ago, the system would refuse to hibernate if
there wasn't a single active swap (I mean, if it found two swaps). Now it
doesn't. So, it might somehow use both... :-?
What I can tell is that in normal use, both partitions are equally filled
(or equally empty).
A note on hibernation: after waking up, some memory remains for ever, it
seems, in swap, so that there is in fact more ram available than before
hibernating. A nice side effect.
In all this thread we have been directing our attention to the swap size
and it effect or not in virtual memory when we are using large RAM, also
its effect in hibernation. I think another important point it is the
need of a large swap when you get a core dump. If a kernel fault cause
the core to dump, this dump go to the swap and avoids corrupting the
file system. I know kernel crashes are rare.
My approach is to keep a large swap. I have to 2GB of RAM and 4GB swap,
until recently swap was not use and very seldom I needed more than 1.4
GB of RAM. Since I started to use beryl and now compiz-fusion :
tdec@amd:~> free -mt
total used free shared buffers
Mem: 2014 1968 46 0 32
-/+ buffers/cache: 1587 426
Swap: 4102 703 3398
Total: 6117 2672 3445
So I may have to add more RAM and perhaps increase the swap :)
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