[SRU][J/K/L:meta-raspi][J/K/L:raspi][PATCH 0/5] raspi-nolpae flavor is pointless nowadays (LP: #2023359)

[Juerg Haefliger]

On Tue, 13 Jun 2023 09:23:41 +0100
Dimitri John Ledkov <dimitri.ledkov at canonical.com> wrote:

> On Tue, 13 Jun 2023 at 09:03, Juerg Haefliger
> <juerg.haefliger at canonical.com> wrote:
> >
> > [Impact]
> >
> > linux-raspi 5.4 in Focal was the first kernel to support Pi 4B, which requires
> > LPAE to be enabled for armhf. Since we currently don't support board-specific
> > kernels but follow a one-kernel-fits-all strategy, the LPAE kernel is also used
> > on Pi 3 and 2 boards. Back then, running an armhf LPAE kernel on a Pi 3/2
> > resulted in additional kernel memory consumption of ~70MB compared to arm64 and
> > non-LPAE kernels. For that reason I decided to introduce a raspi-nolpae flavor
> > which can be used on Pi 3 and 2 (only). That flavor was never officially
> > announced nor installed automatically anywhere. A user has to install it
> > manually. We never had any complaints about armhf kernel memory consumption so
> > never directed anybody at installing this flavor. Therefore I'm assuming it's
> > not being used...
> >
> > Turns out that the early 5.4 kernels were broken and incorrectly initialized a
> > 64MB SWIOTLB buffer which is the reason for the above additional memory
> > consumption. This was fixed here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fcf044891c84e38fc90eb736b818781bccf94e38
> >
> > With this commit, the memory consumption of both the armhf raspi and
> > raspi-nolpae flavor are pretty much on par [1] and there is really no reason
> > anymore to keep the raspi-nolpae flavor around. So let's get rid of it and
> > introduce a transitional package that replaces installed raspi-nolpae packages
> > with raspi packages.
> >
> > [Test Case]
> >
> > Install raspi-nolpae flavor and upgrade to the new kernel and verify that the
> > raspi flavor is installed instead.
> >
> > [Where Problems Could Occur]
> >
> > Only users that have the raspi-nolpae flavor installed are affected. Upgrades,
> > i.e., transitions from raspi-nolpae to raspi could go wrong. It's not expected
> > that there is a user visible difference between running a current raspi-nolpae
> > and raspi kernel flavor.
> >
> > [1]
> > arm64 raspi -- Memory: 815528K/970752K available (13376K kernel code, 2472K rwdata, 4296K rodata, 5504K init, 850K bss, 89688K reserved, 65536K cma-reserved)
> > armhf raspi -- Memory: 835732K/970752K available (12288K kernel code, 1643K rwdata, 3692K rodata, 2048K init, 533K bss, 69484K reserved, 65536K cma-reserved, 118784K highmem)
> > armhf raspi-nolpae -- Memory: 836620K/970752K available (12288K kernel code, 1633K rwdata, 3676K rodata, 1024K init, 511K bss, 68596K reserved, 65536K cma-reserved)
> >  
> 
> Given all of the above, I don't see much point in our
> generic/generic-lpae armhf kernel pair either.
> 
> If you have time, it would be nice to also prepare patches that make
> generic:armhf kernel lpae one, stop building generic-lpae:armhf, make
> generic-lpae:armhf a transitional to generic:armhf. If you don't have
> time to prepare this let me know, and I'll do a separate submission of
> that for mantic onwards.

I'll look into it (and create a separate LP bug). Is this an explicit ACK for
this series then?

...Juerg

 
> >
> > Patches:
> >   1,2: J/K/L linux-meta-raspi
> >   3:   J linux-raspi
> >   4:   K linux-raspi
> >   5:   L linux-raspi
> >
> > --
> > 2.37.2
> >
> > --
> > kernel-team mailing list
> > kernel-team at lists.ubuntu.com
> > https://lists.ubuntu.com/mailman/listinfo/kernel-team  
> 
> 
> 

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