Hi Pingfan, On Wed, Jan 09, 2019 at 09:02:41PM +0800, Pingfan Liu wrote: > On Tue, Jan 8, 2019 at 11:49 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote: > > > > On Tue, Jan 08, 2019 at 05:01:38PM +0800, Baoquan He wrote: > > > Hi Mike, > > > > > > On 01/08/19 at 10:05am, Mike Rapoport wrote: > > > > I'm not thrilled by duplicating this code (yet again). > > > > I liked the v3 of this patch [1] more, assuming we allow bottom-up mode to > > > > allocate [0, kernel_start) unconditionally. > > > > I'd just replace you first patch in v3 [2] with something like: > > > > > > In initmem_init(), we will restore the top-down allocation style anyway. > > > While reserve_crashkernel() is called after initmem_init(), it's not > > > appropriate to adjust memblock_find_in_range_node(), and we really want > > > to find region bottom up for crashkernel reservation, no matter where > > > kernel is loaded, better call __memblock_find_range_bottom_up(). > > > > > > Create a wrapper to do the necessary handling, then call > > > __memblock_find_range_bottom_up() directly, looks better. > > > > What bothers me is 'the necessary handling' which is already done in > > several places in memblock in a similar, but yet slightly different way. > > > > memblock_find_in_range() and memblock_phys_alloc_nid() retry with different > > MEMBLOCK_MIRROR, but memblock_phys_alloc_try_nid() does that only when > > allocating from the specified node and does not retry when it falls back to > > any node. And memblock_alloc_internal() has yet another set of fallbacks. > > > > So what should be the necessary handling in the wrapper for > > __memblock_find_range_bottom_up() ? > > > Well, it is a hard choice. > > BTW, even without any memblock modifications, retrying allocation in > > reserve_crashkerenel() for different ranges, like the proposal at [1] would > > also work, wouldn't it? > > > Yes, it can work. Then is it worth to expose the bottom-up allocation > style beside for hotmovable purpose? Some architectures use bottom-up as a "compatability" mode with bootmem. And, I believe, powerpc and s390 use bottom-up to make some of the allocations close to the kernel. > Thanks, > Pingfan > > [1] http://lists.infradead.org/pipermail/kexec/2017-October/019571.html > > > > > Thanks > > > Baoquan > > > > > > > > > > > diff --git a/mm/memblock.c b/mm/memblock.c > > > > index 7df468c..d1b30b9 100644 > > > > --- a/mm/memblock.c > > > > +++ b/mm/memblock.c > > > > @@ -274,24 +274,14 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size, > > > > * try bottom-up allocation only when bottom-up mode > > > > * is set and @end is above the kernel image. > > > > */ > > > > - if (memblock_bottom_up() && end > kernel_end) { > > > > - phys_addr_t bottom_up_start; > > > > - > > > > - /* make sure we will allocate above the kernel */ > > > > - bottom_up_start = max(start, kernel_end); > > > > - > > > > + if (memblock_bottom_up()) { > > > > /* ok, try bottom-up allocation first */ > > > > - ret = __memblock_find_range_bottom_up(bottom_up_start, end, > > > > + ret = __memblock_find_range_bottom_up(start, end, > > > > size, align, nid, flags); > > > > if (ret) > > > > return ret; > > > > > > > > /* > > > > - * we always limit bottom-up allocation above the kernel, > > > > - * but top-down allocation doesn't have the limit, so > > > > - * retrying top-down allocation may succeed when bottom-up > > > > - * allocation failed. > > > > - * > > > > * bottom-up allocation is expected to be fail very rarely, > > > > * so we use WARN_ONCE() here to see the stack trace if > > > > * fail happens. > > > > > > > > [1] https://lore.kernel.org/lkml/1545966002-3075-3-git-send-email-kernelfans@xxxxxxxxx/ > > > > [2] https://lore.kernel.org/lkml/1545966002-3075-2-git-send-email-kernelfans@xxxxxxxxx/ > > > > > > > > > + > > > > > + return ret; > > > > > +} > > > > > + > > > > > /** > > > > > * __memblock_find_range_top_down - find free area utility, in top-down > > > > > * @start: start of candidate range > > > > > -- > > > > > 2.7.4 > > > > > > > > > > > > > -- > > > > Sincerely yours, > > > > Mike. > > > > > > > > > > > -- > > Sincerely yours, > > Mike. > > > -- Sincerely yours, Mike.
