On 01/08/19 at 05:48pm, Mike Rapoport 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. The page aligning for start and the mirror flag setting, I suppose. > > 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. Get what you mean, seems they are trying to allocate within mirrorred memory region, if fail, try the non-mirrorred region. If kernel data allocation failed, no need to care about if it's movable or not, it need to live firstly. For the bottom-up allocation wrapper, maybe we need do like this too? > > So what should be the necessary handling in the wrapper for > __memblock_find_range_bottom_up() ? > > 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 also looks good. This patch only calls once, seems a simpler line adding. In fact, below one and this patch, both is fine to me, as long as it fixes the problem customers are complaining about. > > [1] http://lists.infradead.org/pipermail/kexec/2017-October/019571.html Thanks Baoquan
