2017-02-15 11:33 GMT+01:00 Peter Robinson <[email protected]>:

> >> We lose some ram on aarch64 due to cma allocation, its something that is
> >> actively being looked at. Anaconda also needs a fair amount of ram
> during
> >> the network install to copy files. Once the install is complete, you
> should
> >> be able to reduce the ram to 2048.
> >
> > 2G not being enough is pretty excessive.  I never had such problems on
> > x86.  Only recently (a year ago or so) I started using 2G for guests, 1G
> > used to be enough even for network installs.
>
> Completely agree, generally if you're doing a anaconda based install
> you need at least 768Mb due to various combinations of installer
> memory usage and selinux applying policies.
>
That's true. If you're looking for smallest memory usage during
installation possible, use NFS installation source (or ISO or ISO over
NFS). That way, install.img (anaconda rootfs - 378MiB large in case of F25)
is mounted directly from nfs shares and packages are also used directly
from NFS, no copying to local / (which is using memory through
device-mapper). HTTP installation consumes the most memory, since it's
copying install.img and other stuff to local / (again in memory). Afaik
RHEL-7 has 1G requirement for NFS installation and 2G for HTTP
installation. The last thing you want to happen is to have OOM during
installation :)


> > I suspect a big factor here is CONFIG_ARM64_64K_PAGES=y.  Raspberry pi
> > 3, with standard fedora kernel (64k pages), minimal install (@core),
> > booted to the shell prompt.  "free" reports ~122MB of memory as used.
> > Same with a self-compiled kernel (4k pages), I get ~44MB of used memory.
> > That is almost factor three!
>
> That is almost the complete factor. It's in fact a combination of 64K
> pages and CMA. The two together mean that the minimum CMA allocated is
> 512Mb of RAM. It's a known problem and one we're looking at different
> ways/options to resolve and working with upstream to do so and
> reconsidering 64K pages in Fedora. We've traditionally gone that route
> due to large enterprise systems and to be in sync with downstreams
> like RHELSA and CentOS in that regard.
>
> Peter
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-- 
Pavel Holica
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