On Fri, Jan 11, 2019 at 2:13 PM Chao Fan <fanc.fnst@xxxxxxxxxxxxxx> wrote: > > On Fri, Jan 11, 2019 at 01:12:51PM +0800, Pingfan Liu wrote: > >This patch identifies the point where memblock alloc start. It has no > >functional. > [...] > >+#ifdef CONFIG_MEMORY_HOTPLUG > >+ /* > >+ * Memory used by the kernel cannot be hot-removed because Linux > >+ * cannot migrate the kernel pages. When memory hotplug is > >+ * enabled, we should prevent memblock from allocating memory > >+ * for the kernel. > >+ * > >+ * ACPI SRAT records all hotpluggable memory ranges. But before > >+ * SRAT is parsed, we don't know about it. > >+ * > >+ * The kernel image is loaded into memory at very early time. We > >+ * cannot prevent this anyway. So on NUMA system, we set any > >+ * node the kernel resides in as un-hotpluggable. > >+ * > >+ * Since on modern servers, one node could have double-digit > >+ * gigabytes memory, we can assume the memory around the kernel > >+ * image is also un-hotpluggable. So before SRAT is parsed, just > >+ * allocate memory near the kernel image to try the best to keep > >+ * the kernel away from hotpluggable memory. > >+ */ > >+ if (movable_node_is_enabled()) > >+ memblock_set_bottom_up(true); > > Hi Pingfan, > > In my understanding, 'movable_node' is based on the that memory near > kernel is considered as in the same node as kernel in high possibility. > > If SRAT has been parsed early, do we still need the kernel parameter > 'movable_node'? Since you have got the memory information about hot-remove, > so I wonder if it's OK to drop 'movable_node', and if memory-hotremove is > enabled, change memblock allocation according to SRAT. > x86_32 still need this logic. Maybe it can be doable later. Thanks, Pingfan > If there is something wrong in my understanding, please let me know. > > Thanks, > Chao Fan > > >+#endif > > init_mem_mapping(); > >+ memblock_set_current_limit(get_max_mapped()); > > > > idt_setup_early_pf(); > > > >@@ -1145,8 +1145,6 @@ void __init setup_arch(char **cmdline_p) > > */ > > mmu_cr4_features = __read_cr4() & ~X86_CR4_PCIDE; > > > >- memblock_set_current_limit(get_max_mapped()); > >- > > /* > > * NOTE: On x86-32, only from this point on, fixmaps are ready for use. > > */ > >-- > >2.7.4 > > > > > > > >
