Ups, linux-api, didn't make it into the CC list. Let's add it here. The cover which will give you some context is here http://lkml.kernel.org/r/20170721143915.14161-1-mhocko@xxxxxxxxxx On Fri 21-07-17 16:39:07, Michal Hocko wrote: > From: Michal Hocko <mhocko@xxxxxxxx> > > Supporting zone ordered zonelists costs us just a lot of code while > the usefulness is arguable if existent at all. Mel has already made > node ordering default on 64b systems. 32b systems are still using > ZONELIST_ORDER_ZONE because it is considered better to fallback to > a different NUMA node rather than consume precious lowmem zones. > > This argument is, however, weaken by the fact that the memory reclaim > has been reworked to be node rather than zone oriented. This means > that lowmem requests have to skip over all highmem pages on LRUs already > and so zone ordering doesn't save the reclaim time much. So the only > advantage of the zone ordering is under a light memory pressure when > highmem requests do not ever hit into lowmem zones and the lowmem > pressure doesn't need to reclaim. > > Considering that 32b NUMA systems are rather suboptimal already and > it is generally advisable to use 64b kernel on such a HW I believe we > should rather care about the code maintainability and just get rid of > ZONELIST_ORDER_ZONE altogether. Keep systcl in place and warn if > somebody tries to set zone ordering either from kernel command line > or the sysctl. > > Changes since v1 > - do not print Default in sysctl handler because our behavior was rather > inconsistent in the past numa_zonelist_order was lowecase while > zonelist_order_name was uppercase so boot time unchanged value woul > print lowercase while updated value could be uppercase. Print "Node" > which is the default instead - Mel > - update documentation - Vlastimil > > Cc: linux-api@xxxxxxxxxxxxxxx > Acked-by: Mel Gorman <mgorman@xxxxxxx> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > --- > Documentation/admin-guide/kernel-parameters.txt | 2 +- > Documentation/sysctl/vm.txt | 4 +- > Documentation/vm/numa | 7 +- > include/linux/mmzone.h | 2 - > kernel/sysctl.c | 2 - > mm/page_alloc.c | 178 +++--------------------- > 6 files changed, 29 insertions(+), 166 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 60530c8490ff..28f1a0f84456 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2724,7 +2724,7 @@ > Allowed values are enable and disable > > numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. > - one of ['zone', 'node', 'default'] can be specified > + 'node', 'default' can be specified > This can be set from sysctl after boot. > See Documentation/sysctl/vm.txt for details. > > diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt > index 48244c42ff52..9baf66a9ef4e 100644 > --- a/Documentation/sysctl/vm.txt > +++ b/Documentation/sysctl/vm.txt > @@ -572,7 +572,9 @@ See Documentation/nommu-mmap.txt for more information. > > numa_zonelist_order > > -This sysctl is only for NUMA. > +This sysctl is only for NUMA and it is deprecated. Anything but > +Node order will fail! > + > 'where the memory is allocated from' is controlled by zonelists. > (This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation. > you may be able to read ZONE_DMA as ZONE_DMA32...) > diff --git a/Documentation/vm/numa b/Documentation/vm/numa > index a08f71647714..a31b85b9bb88 100644 > --- a/Documentation/vm/numa > +++ b/Documentation/vm/numa > @@ -79,11 +79,8 @@ memory, Linux must decide whether to order the zonelists such that allocations > fall back to the same zone type on a different node, or to a different zone > type on the same node. This is an important consideration because some zones, > such as DMA or DMA32, represent relatively scarce resources. Linux chooses > -a default zonelist order based on the sizes of the various zone types relative > -to the total memory of the node and the total memory of the system. The > -default zonelist order may be overridden using the numa_zonelist_order kernel > -boot parameter or sysctl. [see Documentation/admin-guide/kernel-parameters.rst and > -Documentation/sysctl/vm.txt] > +a default Node ordered zonelist. This means it tries to fallback to other zones > +from the same node before using remote nodes which are ordered by NUMA distance. > > By default, Linux will attempt to satisfy memory allocation requests from the > node to which the CPU that executes the request is assigned. Specifically, > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index fc14b8b3f6ce..b849006b20d3 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -895,8 +895,6 @@ int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int, > > extern int numa_zonelist_order_handler(struct ctl_table *, int, > void __user *, size_t *, loff_t *); > -extern char numa_zonelist_order[]; > -#define NUMA_ZONELIST_ORDER_LEN 16 /* string buffer size */ > > #ifndef CONFIG_NEED_MULTIPLE_NODES > > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 655686d546cb..0cbce40f5426 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1553,8 +1553,6 @@ static struct ctl_table vm_table[] = { > #ifdef CONFIG_NUMA > { > .procname = "numa_zonelist_order", > - .data = &numa_zonelist_order, > - .maxlen = NUMA_ZONELIST_ORDER_LEN, > .mode = 0644, > .proc_handler = numa_zonelist_order_handler, > }, > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 80e4adb4c360..b839a90e24c8 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4791,52 +4791,18 @@ static int build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist, > return nr_zones; > } > > - > -/* > - * zonelist_order: > - * 0 = automatic detection of better ordering. > - * 1 = order by ([node] distance, -zonetype) > - * 2 = order by (-zonetype, [node] distance) > - * > - * If not NUMA, ZONELIST_ORDER_ZONE and ZONELIST_ORDER_NODE will create > - * the same zonelist. So only NUMA can configure this param. > - */ > -#define ZONELIST_ORDER_DEFAULT 0 > -#define ZONELIST_ORDER_NODE 1 > -#define ZONELIST_ORDER_ZONE 2 > - > -/* zonelist order in the kernel. > - * set_zonelist_order() will set this to NODE or ZONE. > - */ > -static int current_zonelist_order = ZONELIST_ORDER_DEFAULT; > -static char zonelist_order_name[3][8] = {"Default", "Node", "Zone"}; > - > - > #ifdef CONFIG_NUMA > -/* The value user specified ....changed by config */ > -static int user_zonelist_order = ZONELIST_ORDER_DEFAULT; > -/* string for sysctl */ > -#define NUMA_ZONELIST_ORDER_LEN 16 > -char numa_zonelist_order[16] = "default"; > - > -/* > - * interface for configure zonelist ordering. > - * command line option "numa_zonelist_order" > - * = "[dD]efault - default, automatic configuration. > - * = "[nN]ode - order by node locality, then by zone within node > - * = "[zZ]one - order by zone, then by locality within zone > - */ > > static int __parse_numa_zonelist_order(char *s) > { > - if (*s == 'd' || *s == 'D') { > - user_zonelist_order = ZONELIST_ORDER_DEFAULT; > - } else if (*s == 'n' || *s == 'N') { > - user_zonelist_order = ZONELIST_ORDER_NODE; > - } else if (*s == 'z' || *s == 'Z') { > - user_zonelist_order = ZONELIST_ORDER_ZONE; > - } else { > - pr_warn("Ignoring invalid numa_zonelist_order value: %s\n", s); > + /* > + * We used to support different zonlists modes but they turned > + * out to be just not useful. Let's keep the warning in place > + * if somebody still use the cmd line parameter so that we do > + * not fail it silently > + */ > + if (!(*s == 'd' || *s == 'D' || *s == 'n' || *s == 'N')) { > + pr_warn("Ignoring unsupported numa_zonelist_order value: %s\n", s); > return -EINVAL; > } > return 0; > @@ -4844,16 +4810,10 @@ static int __parse_numa_zonelist_order(char *s) > > static __init int setup_numa_zonelist_order(char *s) > { > - int ret; > - > if (!s) > return 0; > > - ret = __parse_numa_zonelist_order(s); > - if (ret == 0) > - strlcpy(numa_zonelist_order, s, NUMA_ZONELIST_ORDER_LEN); > - > - return ret; > + return __parse_numa_zonelist_order(s); > } > early_param("numa_zonelist_order", setup_numa_zonelist_order); > > @@ -4864,40 +4824,22 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write, > void __user *buffer, size_t *length, > loff_t *ppos) > { > - char saved_string[NUMA_ZONELIST_ORDER_LEN]; > + char *str; > int ret; > - static DEFINE_MUTEX(zl_order_mutex); > > - mutex_lock(&zl_order_mutex); > - if (write) { > - if (strlen((char *)table->data) >= NUMA_ZONELIST_ORDER_LEN) { > - ret = -EINVAL; > - goto out; > - } > - strcpy(saved_string, (char *)table->data); > + if (!write) { > + int len = sizeof("Node"); > + if (copy_to_user(buffer, "Node", len)) > + return -EFAULT; > + return len; > } > - ret = proc_dostring(table, write, buffer, length, ppos); > - if (ret) > - goto out; > - if (write) { > - int oldval = user_zonelist_order; > > - ret = __parse_numa_zonelist_order((char *)table->data); > - if (ret) { > - /* > - * bogus value. restore saved string > - */ > - strncpy((char *)table->data, saved_string, > - NUMA_ZONELIST_ORDER_LEN); > - user_zonelist_order = oldval; > - } else if (oldval != user_zonelist_order) { > - mutex_lock(&zonelists_mutex); > - build_all_zonelists(NULL, NULL); > - mutex_unlock(&zonelists_mutex); > - } > - } > -out: > - mutex_unlock(&zl_order_mutex); > + str = memdup_user_nul(buffer, 16); > + if (IS_ERR(str)) > + return PTR_ERR(str); > + > + ret = __parse_numa_zonelist_order(str); > + kfree(str); > return ret; > } > > @@ -5006,70 +4948,12 @@ static void build_thisnode_zonelists(pg_data_t *pgdat) > */ > static int node_order[MAX_NUMNODES]; > > -static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes) > -{ > - int pos, j, node; > - int zone_type; /* needs to be signed */ > - struct zone *z; > - struct zonelist *zonelist; > - > - zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK]; > - pos = 0; > - for (zone_type = MAX_NR_ZONES - 1; zone_type >= 0; zone_type--) { > - for (j = 0; j < nr_nodes; j++) { > - node = node_order[j]; > - z = &NODE_DATA(node)->node_zones[zone_type]; > - if (managed_zone(z)) { > - zoneref_set_zone(z, > - &zonelist->_zonerefs[pos++]); > - check_highest_zone(zone_type); > - } > - } > - } > - zonelist->_zonerefs[pos].zone = NULL; > - zonelist->_zonerefs[pos].zone_idx = 0; > -} > - > -#if defined(CONFIG_64BIT) > -/* > - * Devices that require DMA32/DMA are relatively rare and do not justify a > - * penalty to every machine in case the specialised case applies. Default > - * to Node-ordering on 64-bit NUMA machines > - */ > -static int default_zonelist_order(void) > -{ > - return ZONELIST_ORDER_NODE; > -} > -#else > -/* > - * On 32-bit, the Normal zone needs to be preserved for allocations accessible > - * by the kernel. If processes running on node 0 deplete the low memory zone > - * then reclaim will occur more frequency increasing stalls and potentially > - * be easier to OOM if a large percentage of the zone is under writeback or > - * dirty. The problem is significantly worse if CONFIG_HIGHPTE is not set. > - * Hence, default to zone ordering on 32-bit. > - */ > -static int default_zonelist_order(void) > -{ > - return ZONELIST_ORDER_ZONE; > -} > -#endif /* CONFIG_64BIT */ > - > -static void set_zonelist_order(void) > -{ > - if (user_zonelist_order == ZONELIST_ORDER_DEFAULT) > - current_zonelist_order = default_zonelist_order(); > - else > - current_zonelist_order = user_zonelist_order; > -} > - > static void build_zonelists(pg_data_t *pgdat) > { > int i, node, load; > nodemask_t used_mask; > int local_node, prev_node; > struct zonelist *zonelist; > - unsigned int order = current_zonelist_order; > > /* initialize zonelists */ > for (i = 0; i < MAX_ZONELISTS; i++) { > @@ -5099,15 +4983,7 @@ static void build_zonelists(pg_data_t *pgdat) > > prev_node = node; > load--; > - if (order == ZONELIST_ORDER_NODE) > - build_zonelists_in_node_order(pgdat, node); > - else > - node_order[i++] = node; /* remember order */ > - } > - > - if (order == ZONELIST_ORDER_ZONE) { > - /* calculate node order -- i.e., DMA last! */ > - build_zonelists_in_zone_order(pgdat, i); > + build_zonelists_in_node_order(pgdat, node); > } > > build_thisnode_zonelists(pgdat); > @@ -5135,11 +5011,6 @@ static void setup_min_unmapped_ratio(void); > static void setup_min_slab_ratio(void); > #else /* CONFIG_NUMA */ > > -static void set_zonelist_order(void) > -{ > - current_zonelist_order = ZONELIST_ORDER_ZONE; > -} > - > static void build_zonelists(pg_data_t *pgdat) > { > int node, local_node; > @@ -5279,8 +5150,6 @@ build_all_zonelists_init(void) > */ > void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone) > { > - set_zonelist_order(); > - > if (system_state == SYSTEM_BOOTING) { > build_all_zonelists_init(); > } else { > @@ -5306,9 +5175,8 @@ void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone) > else > page_group_by_mobility_disabled = 0; > > - pr_info("Built %i zonelists in %s order, mobility grouping %s. Total pages: %ld\n", > + pr_info("Built %i zonelists, mobility grouping %s. Total pages: %ld\n", > nr_online_nodes, > - zonelist_order_name[current_zonelist_order], > page_group_by_mobility_disabled ? "off" : "on", > vm_total_pages); > #ifdef CONFIG_NUMA > -- > 2.11.0 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
