Messages in this thread | | | Subject | Re: [PATCH V8] mm: memory hot-add: hot-added memory can not be added to movable zone by default | From | Changsheng Liu <> | Date | Thu, 5 Nov 2015 11:10:56 +0800 |
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在 2015/11/5 0:31, Dave Hansen 写道: > On 11/04/2015 12:23 AM, liuchangsheng wrote: >> After the user config CONFIG_MOVABLE_NODE, >> When the memory is hot added, should_add_memory_movable() return 0 >> because all zones including ZONE_MOVABLE are empty, >> so the memory that was hot added will be assigned to ZONE_NORMAL, >> and we need using the udev rules to online the memory automatically: >> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", >> ATTR{state}="online_movable" >> The memory block onlined by udev must be adjacent to ZONE_MOVABLE. >> The events of memory section are notified to udev asynchronously, >> so it can not ensure that the memory block onlined by udev is >> adjacent to ZONE_MOVABLE.So it can't ensure memory online always success. >> But we want the whole node to be added to ZONE_MOVABLE by default. > I'm still a bit confused about the whole scenario here. > > Is the core problem: > 1. We add memory in a new node and that node can not be made entirely > movable? As I know, System will not ensure that the node can be made entirely movable if the memory of the node is assigned to ZONE_NORMAL > or > 2. We add memory to an existing zone that has some non-movable memory > and we want the new memory to be movable? It will work if we want to let the memroy movable by using movable_node > >> @@ -1201,6 +1201,9 @@ static int check_hotplug_memory_range(u64 start, u64 size) >> /* >> * If movable zone has already been setup, newly added memory should be check. >> * If its address is higher than movable zone, it should be added as movable. >> + * And if system boots up with movable_node and config CONFIG_MOVABLE_NOD and >> + * added memory does not overlap the zone before MOVABLE_ZONE, >> + * the memory is added as movable. >> * Without this check, movable zone may overlap with other zone. >> */ > This comment is describing what the code does, but is rather sparse on > why. This scenario is pretty convoluted and I can barely make sense of > why it is doing this today while looking at the whole changelog, much > less in a few years when the original changelog will be harder to come by. > > Also please put the comment next to the new if() statement. It's really > hard to match the comment to the code the way you have it now. > >> static int should_add_memory_movable(int nid, u64 start, u64 size) >> @@ -1208,6 +1211,10 @@ static int should_add_memory_movable(int nid, u64 start, u64 size) >> unsigned long start_pfn = start >> PAGE_SHIFT; >> pg_data_t *pgdat = NODE_DATA(nid); >> struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE; >> + struct zone *pre_zone = pgdat->node_zones + (ZONE_MOVABLE - 1); >> + >> + if (movable_node_is_enabled() && (zone_end_pfn(pre_zone) <= start_pfn)) >> + return 1; >> >> if (zone_is_empty(movable_zone)) >> return 0; >> > . >
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