Le 05/06/2016 17:24, emnin...@riseup.net a écrit :
Am Sun, 05 Jun 2016 12:00:01 +0000
schrieb Didier Kryn <k...@in2p3.fr>:
I have a laptop with 16GB of ram. I configured it like this with
the primary goal of not using swap at all. And my /tmp is a tmpfs
with a 4G limit. This allows me to use an SSD as hard disk drive. I
didn't want to swap to an SSD.
I have never been short of ram in 3 years. I have compiled
kernels, GCC, and many other things on this laptop, runing make with
multiple threads; I sometimes got stuck by lack of cpu, never by lack
of ram.
I understand that you want to go further and increase the size
of your /tmp by compressing it. It seems pretty complicated and
probably not worth the burden.
Thank you Didier! Would you mind to put your exact configuration here?
------------- Begin of configuration ------------
HP EliteBook
4 cores Intel(R) Core(TM) i7-3687U CPU @ 2.10GHz
16GB RAM
SSD disk 256GB
fstab:
# <file system> <mount point> <type> <options>
<dump><pass>
# / was on /dev/sda5 during installation
UUID=d91acaa3-5fdc-49e9-9f2b-ba7f3efb33f9 / btrfs noatime
0 1
# /home was on /dev/sda10 during installation
UUID=4709a8c2-825d-43fc-83bb-3b7404feb4aa /home btrfs
noatime 0 2
# /usr was on /dev/sda6 during installation
UUID=05f9f811-b8b1-445f-ac8c-9537a202a9f9 /usr btrfs
noatime 0 2
# /var was on /dev/sda7 during installation
UUID=905a0998-c7fc-4544-a73e-44d8d803602c /var reiserfs
notail,noatime,nosuid 0 2
tmp /tmp tmpfs
size=4G 0 0
My fstab is a mess. I used several partitions not mentionned above
as chroots. I know it's an error to dispatch the OS into several
partitions when using btrfs; won't do it next time.
--------------- End of configuration ------------
Anyway, i went a bit further and around the compressed ram theme.
Given, that i probably will keep the harddrive swap partition
(as i said: for hibernation/s2disk) would it be more useful to use
zswap instead (zswap needs a physical swap device)? And to set the
percentage of ram given to zswap pretty high? (Activate zswap would be
some lines in the bootloader).
I haven't any partition formatted as swap, and, nevertheless,
hibernation works. I realize this just when writing this email and I now
wonder where the hell the kernel saves the system image!
So, using tmpfs as parazyd pointed out, would go to be swapped early
into the compressed swap in ram, when there is no more uncompressed ram
available. Or is it ingenuous thinking?
If i understand correctly, zswap will, when it really comes to the
limits swap out the oldest swap pages to the "pysical" swap device,
zram would kill them (?).
I guess you can swap to both zram and disk. swapon allows you to
give priorities, meaning swap could go to disk only when zram is full.
I would first try to estimate the real need for swap. The common
practice, for years, was to use a swap partition twice the size of the
RAM. Since today a typical RAM is around 4GB, this puts a limit of 12GB
total. But you've got 16! Without swap, you have more than a typical
laptop with swap.
Didier
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