Messages in this thread | | | From | Michael Nazzareno Trimarchi <> | Date | Mon, 19 Sep 2022 11:57:30 +0200 | Subject | Re: Correlation CMA size and FORCE_MAX_ZONEORDER |
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Hi
On Mon, Sep 19, 2022 at 11:31 AM David Hildenbrand <david@redhat.com> wrote: > > On 19.09.22 11:17, Michael Nazzareno Trimarchi wrote: > > Hi David > > > > On Mon, Sep 19, 2022 at 10:38 AM David Hildenbrand <david@redhat.com> wrote: > >> > >> On 15.09.22 23:36, Michael Nazzareno Trimarchi wrote: > >>> Hi all > >> > >> Hi, > >> > >>> > >>> Working on a small device with 128MB of memory and using imx_v6_v7 > >>> defconfig I found that CMA_SIZE_MBYTES, CMA_SIZE_PERCENTAGE > >>> are not respected. The calculation done does not allow the requested > >>> size. I think that this should be somehow documented and described but > >>> I did not > >>> find the documentation. Does it work this way? > >>> > >>> With CMA_SIZE of 8MB I need to have FORCE_MAX_ZONEORDER=12 if I have > >>> the default FORCE_MAX_ZONEORDER=14 the min size is 32Mb > >> > >> The underlying constraint is that CMA regions require a certain minimum > >> alignment+size. They cannot be arbitrarily in size. > >> > >> CMA_MIN_ALIGNMENT_BYTES expresses that, and corresponds in upstream > >> kernels to the size of a single pageblock. > >> > >> In previous kernels, it used to be the size of the largest buddy > >> allocation granularity (derived from MAX_ORDER, derived from > >> FORCE_MAX_ZONEORDER). > >> > >> On upstream kernels, the FORCE_MAX_ZONEORDER constraint should no longer > >> apply. On most archs, the minimum alignment+size should be 2 MiB > >> (x86-64, aarch64 with 4k base pages) -- the size of a single pageblock. > >> > >> So far the theory. Are you still running into this limitation on > >> upstream kernels? > >> > > > > I can run 6-rc2 on my board. I test again but according to it, if I > > put 4M as CMA in cma=4M in boot > > parameters, the result is 32Mb of CMA. Apart of that seems that > > process lime tiny membench can not even start > > to mblock memory > > > > The CMA alignemnt change went into v5.19. If "cma=4M" still gives you > > 4M, can you post /proc/meminfo and the early console output? >
cat /proc/cmdline cma=4M mtdparts=gpmi-nand:4m(nandboot),1m(env),24m(kernel),1m(nanddtb),-(rootfs) root=ubi0:root rw ubi.mtd=ro otfs rootfstype=ubifs rootwait=1 # cat /proc/meminfo MemTotal: 109560 kB MemFree: 56084 kB MemAvailable: 56820 kB Buffers: 0 kB Cached: 39680 kB SwapCached: 0 kB Active: 44 kB Inactive: 644 kB Active(anon): 44 kB Inactive(anon): 644 kB Active(file): 0 kB Inactive(file): 0 kB Unevictable: 39596 kB Mlocked: 0 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 109560 kB LowFree: 56084 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 0 kB Writeback: 0 kB AnonPages: 628 kB Mapped: 1480 kB Shmem: 84 kB KReclaimable: 4268 kB Slab: 8456 kB SReclaimable: 4268 kB SUnreclaim: 4188 kB KernelStack: 392 kB PageTables: 88 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 54780 kB Committed_AS: 1876 kB VmallocTotal: 901120 kB VmallocUsed: 2776 kB VmallocChunk: 0 kB Percpu: 72 kB CmaTotal: 32768 kB CmaFree: 32484 kB # uname -a Linux buildroot 6.0.0-rc5 #20 SMP Mon Sep 19 11:51:26 CEST 2022 armv7l GNU/Linux #
Then here https://pastebin.com/6MUB2VBM dmesg
CONFIG_ARM_MODULE_PLTS=y CONFIG_FORCE_MAX_ZONEORDER=14 CONFIG_ALIGNMENT_TRAP=y ... CONFIG_CMA CONFIG_CMA_AREAS=7 ...
CONFIG_CMA_SIZE_MBYTES=8 CONFIG_CMA_SIZE_SEL_MBYTES=y
Michael
> > -- > Thanks, > > David / dhildenb > -- Michael Nazzareno Trimarchi Co-Founder & Chief Executive Officer M. +39 347 913 2170 michael@amarulasolutions.com __________________________________
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