2017-02-15 11:33 GMT+01:00 Peter Robinson <pbrobinson@gmail.com>:
>> 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