On 08/11/2014 12:18 AM, Zhang Zhen wrote: > +What: /sys/devices/system/memory/memoryX/zone_to_online > +Date: July 2014 > +Contact: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx> > +Description: > + The file /sys/devices/system/memory/memoryX/zone_to_online > + is read-only and is designed to show which zone this memory block can > + be onlined to. > +Users: hotplug memory remove tools > + http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils I went and looked there. It redirects immediately to: https://www.ibm.com/developerworks/community/wikis/home?lang=en Where a search for "hotplug memory remove tools" finds nothing. What hardware and hypervisor are you looking at this for? > What: /sys/devices/system/memoryX/nodeY > Date: October 2009 > Contact: Linux Memory Management list <linux-mm@xxxxxxxxx> > diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt > index 45134dc..09e3d37 100644 > --- a/Documentation/memory-hotplug.txt > +++ b/Documentation/memory-hotplug.txt > @@ -155,6 +155,7 @@ Under each memory block, you can see 4 files: > /sys/devices/system/memory/memoryXXX/phys_device > /sys/devices/system/memory/memoryXXX/state > /sys/devices/system/memory/memoryXXX/removable > +/sys/devices/system/memory/memoryXXX/zone_to_online > > 'phys_index' : read-only and contains memory block id, same as XXX. > 'state' : read-write > @@ -170,6 +171,8 @@ Under each memory block, you can see 4 files: > block is removable and a value of 0 indicates that > it is not removable. A memory block is removable only if > every section in the block is removable. > +'zone_to_online' : read-only: designed to show which zone this memory block > + can be onlined to. Zone to online makes it sound like this is the zone that is about to be onlined, not the section. "zone_online_to" would be a bit more appropriate, or maybe "online_zones_possible". Isn't it possible to have more than a single zone show up? > NOTE: > These directories/files appear after physical memory hotplug phase. > @@ -408,7 +411,6 @@ node if necessary. > - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like > sysctl or new control file. > - showing memory block and physical device relationship. > - - showing memory block is under ZONE_MOVABLE or not > - test and make it better memory offlining. > - support HugeTLB page migration and offlining. > - memmap removing at memory offline. > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index a2e13e2..044353c 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -373,11 +373,70 @@ static ssize_t show_phys_device(struct device *dev, > return sprintf(buf, "%d\n", mem->phys_device); > } > > +static ssize_t show_zone_to_online(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct memory_block *mem = to_memory_block(dev); > + unsigned long start_pfn, end_pfn; > + unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; > + struct page *first_page; > + struct zone *zone, *zone_prev, *zone_next; > + > + first_page = pfn_to_page(mem->start_section_nr << PFN_SECTION_SHIFT); Is there something wrong with section_nr_to_pfn()? > + start_pfn = page_to_pfn(first_page); Nit: Why do pfn_to_page() then page_to_pfn() immediately? > + end_pfn = start_pfn + nr_pages; > + > + /*The block contains more than one zone can not be offlined.*/ Do you mean onlined? > + if (!test_pages_in_a_zone(start_pfn, end_pfn)) > + return sprintf(buf, "NULL\n"); "(none)" is a bit more normal nomenclature in sysfs. > + zone = page_zone(first_page); > + > + /*The mem block is the last block of memory.*/ > + if (!pfn_valid(end_pfn + 1)) { This check only looks for a *hole* in the page after this block ends. It does not check all of the other pages *above* end_pfn+1, which would be needed to guarantee that this is "the last block of memory". > +#ifdef CONFIG_HIGHMEM > + if (zone_idx(zone) == ZONE_HIGHMEM) > + return sprintf(buf, "%s %s\n", zone->name, (zone + 1)->name); > +#else > + if (zone_idx(zone) == ZONE_NORMAL) > + return sprintf(buf, "%s %s\n", zone->name, (zone + 1)->name); > +#endif > + if (zone_idx(zone) == ZONE_MOVABLE) { > + if (pfn_valid(start_pfn - nr_pages)) { > + zone_prev = page_zone(first_page - nr_pages); > + if (zone_idx(zone_prev) != ZONE_MOVABLE) > + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); > + } else > + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); > + } > + return sprintf(buf, "%s\n", zone->name); > + > + } > + > + zone_next = page_zone(first_page + nr_pages + 1); Is the +1 necessary? It doesn't matter in practice since we don't have single-page zones, but it is a bit confusing. Seems to me like this will get page[1] instead of page[0]. Furthermore, this might cross a section boundary where 'struct page' arithmetic is not guaranteed not work. That makes it _definitely_ broken. > +#ifdef CONFIG_HIGHMEM > + if (zone_idx(zone) == ZONE_HIGHMEM && zone_idx(zone_next) == ZONE_MOVABLE) > + return sprintf(buf, "%s %s\n", zone->name, zone_next->name); > +#else > + if (zone_idx(zone) == ZONE_NORMAL && zone_idx(zone_next) == ZONE_MOVABLE) > + return sprintf(buf, "%s %s\n", zone->name, zone_next->name); > +#endif > + if (zone_idx(zone) == ZONE_MOVABLE) { > + if (pfn_valid(start_pfn - nr_pages)) { > + zone_prev = page_zone(first_page - nr_pages); > + if (zone_idx(zone_prev) != ZONE_MOVABLE) > + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); > + } else > + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); > + } > + return sprintf(buf, "%s\n", zone->name); > +} Can you please work to clean this up a bit. I think it's quite a mess. I see two #ifdefs in a .c file, and a fairly large block of (virtually) uncommented and copy-n-pasted code. The two copies of this: >> + if (zone_idx(zone) == ZONE_MOVABLE) { >> + if (pfn_valid(start_pfn - nr_pages)) { >> + zone_prev = page_zone(first_page - nr_pages); >> + if (zone_idx(zone_prev) != ZONE_MOVABLE) >> + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); >> + } else >> + return sprintf(buf, "%s %s\n", zone->name, (zone - 1)->name); >> + } >> + return sprintf(buf, "%s\n", zone->name); are identical except for the indentation. This is also supposed to be enumerating rules that are enforced by some other bit of code. There are, as far as I can see, no calls in to that other code, or comments about what code it depends on. To me, this looks like an invitation for the two copies to diverge. -- 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/ . 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