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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Mike Rapoport <rppt@linux.ibm.com>, linux-mm@kvack.org
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Subject: Re: [PATCH v2 10/21] memblock: refactor internal allocation functions
In-Reply-To: <1548057848-15136-11-git-send-email-rppt@linux.ibm.com>
References: <1548057848-15136-1-git-send-email-rppt@linux.ibm.com> <1548057848-15136-11-git-send-email-rppt@linux.ibm.com>
Date:   Sun, 03 Feb 2019 20:39:20 +1100
Message-ID: <87ftt5nrcn.fsf@concordia.ellerman.id.au>
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Mike Rapoport <rppt@linux.ibm.com> writes:

> Currently, memblock has several internal functions with overlapping
> functionality. They all call memblock_find_in_range_node() to find free
> memory and then reserve the allocated range and mark it with kmemleak.
> However, there is difference in the allocation constraints and in fallback
> strategies.
>
> The allocations returning physical address first attempt to find free
> memory on the specified node within mirrored memory regions, then retry on
> the same node without the requirement for memory mirroring and finally fall
> back to all available memory.
>
> The allocations returning virtual address start with clamping the allowed
> range to memblock.current_limit, attempt to allocate from the specified
> node from regions with mirroring and with user defined minimal address. If
> such allocation fails, next attempt is done with node restriction lifted.
> Next, the allocation is retried with minimal address reset to zero and at
> last without the requirement for mirrored regions.
>
> Let's consolidate various fallbacks handling and make them more consistent
> for physical and virtual variants. Most of the fallback handling is moved
> to memblock_alloc_range_nid() and it now handles node and mirror fallbacks.
>
> The memblock_alloc_internal() uses memblock_alloc_range_nid() to get a
> physical address of the allocated range and converts it to virtual address.
>
> The fallback for allocation below the specified minimal address remains in
> memblock_alloc_internal() because memblock_alloc_range_nid() is used by CMA
> with exact requirement for lower bounds.

This is causing problems on some of my machines.

I see NODE_DATA allocations falling back to node 0 when they shouldn't,
or didn't previously.

eg, before:

57990190: (116011251): numa:   NODE_DATA [mem 0xfffe4980-0xfffebfff]
58152042: (116373087): numa:   NODE_DATA [mem 0x8fff90980-0x8fff97fff]

after:

16356872061562: (6296877055): numa:   NODE_DATA [mem 0xfffe4980-0xfffebfff]
16356872079279: (6296894772): numa:   NODE_DATA [mem 0xfffcd300-0xfffd497f]
16356872096376: (6296911869): numa:     NODE_DATA(1) on node 0


On some of my other systems it does that, and then panics because it
can't allocate anything at all:

[    0.000000] numa:   NODE_DATA [mem 0x7ffcaee80-0x7ffcb3fff]
[    0.000000] numa:   NODE_DATA [mem 0x7ffc99d00-0x7ffc9ee7f]
[    0.000000] numa:     NODE_DATA(1) on node 0
[    0.000000] Kernel panic - not syncing: Cannot allocate 20864 bytes for node 16 data
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc4-gccN-next-20190201-gdc4c899 #1
[    0.000000] Call Trace:
[    0.000000] [c0000000011cfca0] [c000000000c11044] dump_stack+0xe8/0x164 (unreliable)
[    0.000000] [c0000000011cfcf0] [c0000000000fdd6c] panic+0x17c/0x3e0
[    0.000000] [c0000000011cfd90] [c000000000f61bc8] initmem_init+0x128/0x260
[    0.000000] [c0000000011cfe60] [c000000000f57940] setup_arch+0x398/0x418
[    0.000000] [c0000000011cfee0] [c000000000f50a94] start_kernel+0xa0/0x684
[    0.000000] [c0000000011cff90] [c00000000000af70] start_here_common+0x1c/0x52c
[    0.000000] Rebooting in 180 seconds..


So there's something going wrong there, I haven't had time to dig into
it though (Sunday night here).

cheers