[systemd-devel] [PATCH] udev: Adding zram to inappropriate block device

[Greg KH]

On Thu, Feb 06, 2014 at 01:31:37AM +0100, Zbigniew Jędrzejewski-Szmek wrote:
> Patch applied.
> 
> On Mon, Feb 03, 2014 at 10:33:37AM +0000, "Jóhann B. Guðmundsson" wrote:
> > On 02/03/2014 09:36 AM, Holger Schurig wrote:
> > >>with unit type ending in .zswap
> > >No, not another unit type. Instead better amend .swap unit types to
> > >also know about ZRAM.
> > >
> > >However, isn't this a bit early? Shouldn't move ZRAM first move out of staging?
> > 
> > Ofcourse but when it does move out of staging we could have sorted
> > this implementation detail out which basically boils down to where
> > to set the partition sizes for the zram partitions (
> > tmpfiles.d/zram-conf or /etc/zram.d/zram-conf )
> > 
> > Do we want a script that basically just set this size based on
> > available memory per core in the udev rule.
> > 
> > factor=25
> > num_cpus=$(grep -c processor /proc/cpuinfo)
> > memtotal=$(grep MemTotal /proc/meminfo | sed 's/[^0-9]\+//g')
> > mem_by_cpu=$(($memtotal/$num_cpus*$factor/100*1024))
> > echo $mem_by_cpu
> 
> [Side note: I'm reading Documentation/blockdev/zram.txt...
> It says "1. modprobe zram num_devices=4". I can't help thinking that
> we went over this with /dev/loop-control and others... Since this
> is a new interface, why does it repeat the same pitfall of not
> having a control device?]

We can always change this now, quick, before 3.14 is out.

What would a control device help with here?

> Wouldn't it be simplest to have a parameter in /etc/fstab, like
> x.zram-disk-size=XXX, which swapon would write to /sys/block/.../disksize?
> This would make everything centralized and "synchronous" from the point
> of view of the administrator.

Module paramaters are under control of the admin, but they are a mess,
I agree.

thanks,

greg k-h