** Changed in: linux (Ubuntu Eoan)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1823753
Title:
arm64: cma_alloc errors at boot
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Disco:
In Progress
Status in linux source package in Eoan:
Fix Committed
Bug description:
[Impact]
We enabled CONFIG_DMA_CMA to fix bug 1803206, but that led to a regression
on other arm64 systems that began spewing these messages on boot - sometimes
> 10K of them:
[ 19.534097] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
[ 19.534109] cma: cma_alloc: alloc failed, req-size: 16 pages, ret: -12
[ 19.534113] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
[ 19.534126] cma: cma_alloc: alloc failed, req-size: 16 pages, ret: -12
[ 19.534130] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
[ 19.534142] cma: cma_alloc: alloc failed, req-size: 16 pages, ret: -12
[ 19.534146] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
[ 19.534157] cma: cma_alloc: alloc failed, req-size: 16 pages, ret: -12
[ 19.534161] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
[ 19.534173] cma: cma_alloc: alloc failed, req-size: 16 pages, ret: -12
[ 19.534177] cma: cma_alloc: alloc failed, req-size: 64 pages, ret: -12
In a previous SRU (bug 1828092), we worked around this by just rate-
limiting these messages. These are "err" priority messages though, so
even a lower number of them is still disconcerting.
[Fix]
1) Bump up the amount of available CMA on arm64 to 32M (same as upstream
defconfig)
2) A patch-set from linux-next that redirects dma-direct contiguous
allocations to alloc_pages() for single page allocations (single pages are by
definition contiguous), avoiding CMA usage/fragmentation.
[Test Case]
dmesg | grep "cma_alloc: alloc failed"
Some system configs will still have some of these errors even after this fix
- but this should reduce them significantly. Per-driver optimizations can be
used to make further improvements, but we should track those in other bugs.
[Regression Risk]
Tested on a HiSilicon D06 and HP m400 (Hi1620 & X-Gene arm64).
Regression tested on:
- Raspberry Pi 3B (see Comment #22)
- Power9 system (ppc64el)
- z/VM instance (s390x)
- Intel Centerton system (amd64)
Test builds are staged at http://ppa.launchpad.net/~dannf/ubuntu/cma
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