Re: [PATCH v2 10/21] memblock: refactor internal allocation functions

Mike Rapoport
2019-02-03T10:04:28Z

On Sun, Feb 03, 2019 at 08:39:20PM +1100, Michael Ellerman wrote:
> 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).

I'll try to see if I can reproduce it with qemu.

> cheers
>

--
Sincerely yours,
Mike.