Messages in this thread | | | Date | Thu, 27 Mar 2008 13:54:52 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: Trying to make use of hotplug memory for xen balloon driver |
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KAMEZAWA Hiroyuki wrote: > On Wed, 26 Mar 2008 22:57:57 -0700 > Jeremy Fitzhardinge <jeremy@goop.org> wrote: > > >> Ah, I see what it is. I wasn't trying to add enough memory. It adds in >> units of SECTION_SIZE_BITS, which is 2^30 on 32-bit PAE. When I >> increase the initial balloon extension to PAGES_PER_SECTION pages, I >> make some more progress: >> >> xen_balloon: Initialising balloon driver. >> trying to reserve 262144 pages (1073741824 bytes) for balloon >> bootmem alloc of 147456 bytes failed! >> Kernel panic - not syncing: Out of memory >> Pid: 1, comm: swapper Not tainted 2.6.25-rc7-x86-latest.git-dirty #361 >> [<c01299dc>] panic+0x49/0x102 >> [<c0647c3c>] __alloc_bootmem+0x24/0x29 >> [<c0647c6d>] __alloc_bootmem_node+0x2c/0x34 >> [<c044bd97>] zone_wait_table_init+0x45/0x95 >> [<c0467258>] init_currently_empty_zone+0x1d/0xaa >> [<c01738ea>] __add_pages+0x88/0xdb >> [<c011c1a5>] arch_add_memory+0x25/0x2b >> [<c01737a9>] add_memory_resource+0x2f/0x36 >> [<c064e487>] balloon_init+0x1b8/0x2b9 >> [<c0635495>] kernel_init+0x137/0x292 >> [<c063535e>] ? kernel_init+0x0/0x292 >> [<c063535e>] ? kernel_init+0x0/0x292 >> [<c0108b67>] kernel_thread_helper+0x7/0x10 >> ======================= >> >> >> What's the rationale for setting SECTION_SIZE_BITS to 30? Seems like a >> fairly large chunk. >> >> > At first, I believe usual DIMM size is bigger than SECTION_SIZE_BITS. This is > designed for hardware-based hotplug. > > If you want to use memory-hotplug for virtualized enviroment, it's good to make > this to be smaller chunk. Powerpc/IBM lpar uses 16MB chunk. > > It's a trade-off between section mainainance cost v.s. size of plugged memory. > please find the best.
Hm, I tried reducing it to 2^28 (=256M), but I get a compilation failure:
CC arch/x86/kernel/asm-offsets.s In file included from /home/jeremy/hg/xen/paravirt/linux/include/linux/suspend.h:11, from /home/jeremy/hg/xen/paravirt/linux/arch/x86/kernel/asm-offsets_32.c:11, from /home/jeremy/hg/xen/paravirt/linux/arch/x86/kernel/asm-offsets.c:2: /home/jeremy/hg/xen/paravirt/linux/include/linux/mm.h:458:2: error: #error SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH > FLAGS_RESERVED make[3]: *** [arch/x86/kernel/asm-offsets.s] Error 1
2^29 works.
J
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