Hi Peter, Peter Teoh <htmldeveloper@xxxxxxxxx> writes: > http://www.gossamer-threads.com/lists/linux/kernel/954421?page=last > > Someone please help me out: > > a. What is pgdat? From header - I read but cannot find the > motivation behind all these: > > /* > * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM > * (mostly NUMA machines?) to denote a higher-level memory zone than the > * zone denotes. > * > * On NUMA machines, each NUMA node would have a pg_data_t to describe > * it's memory layout. > * > * Memory statistics and page replacement data structures are > maintained on a > * per-zone basis. > */ > struct bootmem_data; > typedef struct pglist_data { > struct zone node_zones[MAX_NR_ZONES]; > struct zonelist node_zonelists[MAX_ZONELISTS]; > int nr_zones; > #ifdef CONFIG_FLAT_NODE_MEM_MAP > struct page *node_mem_map; > #endif > struct bootmem_data *bdata; > #ifdef CONFIG_MEMORY_HOTPLUG > /* > * Must be held any time you expect node_start_pfn, > node_present_pages > * or node_spanned_pages stay constant. Holding this will also > * guarantee that any pfn_valid() stays that way. > * > * Nests above zone->lock and zone->size_seqlock. > */ > spinlock_t node_size_lock; > #endif > unsigned long node_start_pfn; > unsigned long node_present_pages; /* total number of physical > pages */ > unsigned long node_spanned_pages; /* total size of physical page > range, including holes */ > int node_id; > wait_queue_head_t kswapd_wait; > struct task_struct *kswapd; > int kswapd_max_order; > } pg_data_t; > > And why not u have to remove it? For what purposes? Why memory > hotplug needs this feature off? > > And as today I can still can see the structure, so is the patch > reversed? If so, then the memory hotplug must have got a > replacement/substitution for this removal of pgdat - is that correct? It's not about removal of this structure but a removal of physical nodes when you hot-unplug the memory. The kernel has to cope with that (unuse the page frames of the node about to be removed). Hannes -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
