Mounting /tmp in RAM and using zram
Sweyn78
discovered some cool things about filesystems and the fstab. Now, I
am not sure whether this is already done in Chromium OS< but if it is
not, I would highly recommend doing this:
*Mounting zram (zram is a compressed swap space inside of your system
RAM and functions as normal RAM, except that it has a higher carrying
capacity and requires some CPU usage)
*Mounting /tmp as tmpfs (when normal RAM runs-out, the computer will
swap to the zrams first, and the hd/ssd second)
Alternatively, you could use a ResierFS, Resier4, or ext2 partition
for /tmp and turn-off everything that has to do with preventing data-
loss. (I could post the mount options I use for my ReserFS /tmp if
necessary)
This will allow maximum browsing speed without wasting system
resources (think about it: by default in most distros, you're storing /
tmp files on a journaling filesystem, which is completely
unecessary). On an ssd, where reads and writes come at a premium, it
is especially important to try and reduce the amount of reads/writes
to the disk. If zram turns you off andyou really wanted to get
creative, you could use btrfs's subvolumes so that /tmp wouldn't be
fixed in size or result in a pocket of freespace between it and other
partitions.
Happy fstabing! :)
Olof Johansson
On Tue, Dec 20, 2011 at 8:23 PM, Sweyn78 <swe...@gmail.com> wrote:
[...]
> *Mounting /tmp as tmpfs (when normal RAM runs-out, the computer will
> swap to the zrams first, and the hd/ssd second)
We already do this.
> This will allow maximum browsing speed without wasting system
> resources (think about it: by default in most distros, you're storing /
> tmp files on a journaling filesystem, which is completely
> unecessary).
Performance suggestions are good, but performance suggestions with
hard benchmark data to back it up are even better. There are some
autotests for running some of the chrome browsing benchmarks as part
of the autotest suite that you can build and run against your own
build of Chromium OS to collect this data. See
http://www.chromium.org/developers/testing/page-cyclers and the
pagecycler autotests for more info.
> On an ssd, where reads and writes come at a premium, it
> is especially important to try and reduce the amount of reads/writes
> to the disk.
At a premium compared to what? SSDs are much faster than rotating
media for all operations.
-Olof
Jeremy Bicha
>> On an ssd, where reads and writes come at a premium, it
>> is especially important to try and reduce the amount of reads/writes
>> to the disk.
>
> At a premium compared to what? SSDs are much faster than rotating
> media for all operations.
I assume he's referring to the commonly held myth that if you have to
pay careful attention to how much your write to your SSD if you don't
want your SSD to fail soon because you exceeded its write limit.
Jeremy
Olof Johansson
Ah. That is unfortunately not a myth at all, in particular not for
consumer-grade devices such as the ones used in Chromebooks.
Fortunately the workloads we have are still well behaved in that sense
though, so we're not exposed to some of those problems.
-Olof
Mike Frysinger
use /tmp for few things, and none seem to be very large.
-mike
Sonny Rao
actually swap. Also, if we did use actual swap to disk, we'd have to
encrypt it which would increase the overhead.
People on the team have investigated swap to zram for low memory
devices but as of now we have decided not to implement it yet since
all of our shipping devices currently have 2GiB of memory which seems
to be enough for "normal" uses.
That said, someone using Chromium OS could probably set it up fairly
easily if they wanted to or needed it.
Sonny
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BigRedFed
Sonny Rao
with CONFIG_ZRAM=y and CONFIG_SWAP=y and install it.
If you did that, then on the new kernel, create a zram device, format
for swap, then turn it on:
echo $size > /sys/block/zram0/disksize
mkswap /dev/zram0
swapon /dev/zram0
disclaimer: I haven't tried this myself :-)
