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    SubjectRe: [patch] mm: node-setup agnostic free_bootmem()
    Date
    Hi,

    "Yinghai Lu" <yhlu.kernel@gmail.com> writes:

    > On Wed, Apr 30, 2008 at 3:50 AM, Johannes Weiner <hannes@saeurebad.de> wrote:
    >>
    >> Hi,
    >>
    >> "Yinghai Lu" <yhlu.kernel@gmail.com> writes:
    >>
    >> > On Mon, Apr 28, 2008 at 12:11 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
    >> >>
    >> >> On Mon, Apr 28, 2008 at 9:54 AM, Johannes Weiner <hannes@saeurebad.de> wrote:
    >> >> > Hi Yinghai,
    >> >> >
    >> >> >
    >> >> >
    >> >> > "Yinghai Lu" <yhlu.kernel@gmail.com> writes:
    >> >> >
    >> >> > > On Sun, Apr 27, 2008 at 5:40 PM, Ingo Molnar <mingo@elte.hu> wrote:
    >> >> > >>
    >> >> > >> * Johannes Weiner <hannes@saeurebad.de> wrote:
    >> >> > >>
    >> >> > >> > > so i very much agree that your changes are cleaner, i just wanted to
    >> >> > >> > > have one that has all the fixes included.
    >> >> > >> >
    >> >> > >> > I had planned this to be another patch because there are more then one
    >> >> > >> > boundary check I wanted to tighten. I can merge them though if you
    >> >> > >> > like.
    >> >> > >>
    >> >> > >> no, better to have them in separate patches.
    >> >> > >>
    >> >> > >> > > Would you like to post a patch against current -git or should i
    >> >> > >> > > extract the cleaner reserve_bootmem() from your previous patch?
    >> >> > >> >
    >> >> > >> > I just moved and have only sporadic internet access and free time
    >> >> > >> > slots available. Would be nice if you could do it!
    >> >> > >>
    >> >> > >> sure, find the merged patch below, against latest -git, boot-tested on
    >> >> > >> x86. Is this what you had in mind?
    >> >> > >>
    >> >> > >> Ingo
    >> >> > >>
    >> >> > >> ---------------->
    >> >> > >> Subject: mm: node-setup agnostic free_bootmem()
    >> >> > >> From: Johannes Weiner <hannes@saeurebad.de>
    >> >> > >> Date: Wed, 16 Apr 2008 13:36:31 +0200
    >> >> > >>
    >> >> > >> Make free_bootmem() look up the node holding the specified address
    >> >> > >> range which lets it work transparently on single-node and multi-node
    >> >> > >> configurations.
    >> >> > >>
    >> >> > >> If the address range exceeds the node range, it well be marked free
    >> >> > >> across node boundaries, too.
    >> >> > >>
    >> >> > >> Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
    >> >> > >> CC: Andi Kleen <andi@firstfloor.org>
    >> >> > >> CC: Yinghai Lu <yhlu.kernel@gmail.com>
    >> >> > >> CC: Yasunori Goto <y-goto@jp.fujitsu.com>
    >> >> > >> CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    >> >> > >> CC: Christoph Lameter <clameter@sgi.com>
    >> >> > >> CC: Andrew Morton <akpm@linux-foundation.org>
    >> >> > >> Signed-off-by: Ingo Molnar <mingo@elte.hu>
    >> >> > >> ---
    >> >> > >> mm/bootmem.c | 27 +++++++++++++++++++++++++--
    >> >> > >> 1 file changed, 25 insertions(+), 2 deletions(-)
    >> >> > >>
    >> >> > >> Index: linux-x86.q/mm/bootmem.c
    >> >> > >> ===================================================================
    >> >> > >> --- linux-x86.q.orig/mm/bootmem.c
    >> >> > >> +++ linux-x86.q/mm/bootmem.c
    >> >> > >> @@ -493,8 +493,31 @@ int __init reserve_bootmem(unsigned long
    >> >> > >> void __init free_bootmem(unsigned long addr, unsigned long size)
    >> >> > >> {
    >> >> > >> bootmem_data_t *bdata;
    >> >> > >> - list_for_each_entry(bdata, &bdata_list, list)
    >> >> > >> - free_bootmem_core(bdata, addr, size);
    >> >> > >> + unsigned long pos = addr;
    >> >> > >> + unsigned long partsize = size;
    >> >> > >> +
    >> >> > >> + list_for_each_entry(bdata, &bdata_list, list) {
    >> >> > >> + unsigned long remainder = 0;
    >> >> > >> +
    >> >> > >> + if (pos < bdata->node_boot_start)
    >> >> > >> + continue;
    >> >> > >> +
    >> >> > >> + if (PFN_DOWN(pos + partsize) > bdata->node_low_pfn) {
    >> >> > >> + remainder = PFN_DOWN(pos + partsize) - bdata->node_low_pfn;
    >> >> > >> + partsize -= remainder;
    >> >> > >> + }
    >> >> > >> +
    >> >> > >> + free_bootmem_core(bdata, pos, partsize);
    >> >> > >> +
    >> >> > >> + if (!remainder)
    >> >> > >> + return;
    >> >> > >> +
    >> >> > >> + pos = PFN_PHYS(bdata->node_low_pfn + 1);
    >> >> > >> + }
    >> >> > >> + printk(KERN_ERR "free_bootmem: request: addr=%lx, size=%lx, "
    >> >> > >> + "state: pos=%lx, partsize=%lx\n", addr, size,
    >> >> > >> + pos, partsize);
    >> >> > >> + BUG();
    >> >> > >> }
    >> >> > >>
    >> >> > >> unsigned long __init free_all_bootmem(void)
    >> >> > >>
    >> >> > >
    >> >> > > it will not work with cross nodes.
    >> >> > >
    >> >> > > for example: node 0: 0-2g, 4-6g, node1: 2-4g, 6-8g.
    >> >> > > and if ramdisk sit cross 2G boundary. you will only free the range
    >> >> > > before 2g.
    >> >> >
    >> >> > Yes, you stated that several times but this is not a technical argument:
    >> >> > These setups are afaik not yet supported by the kernel at all. And you
    >> >> > could not explain the node layout with the patch that implements support
    >> >> > for these configurations.
    >> >>
    >> >> I looked at Suresh's patch, and it still only has one bdata for one node.
    >> >
    >> > Suresh's patch already in the Linus tree.
    >> > commit 6ec6e0d9f2fd7cb6ca6bc3bfab5ae7b5cdd8c36f
    >> > Author: Suresh Siddha <suresh.b.siddha@intel.com>
    >> > Date: Tue Mar 25 10:14:35 2008 -0700
    >> >
    >> > srat, x86: add support for nodes spanning other nodes
    >> >
    >> > For example, If the physical address layout on a two node system with 8 GB
    >> > memory is something like:
    >> > node 0: 0-2GB, 4-6GB
    >> > node 1: 2-4GB, 6-8GB
    >> >
    >> > Current kernels fail to boot/detect this NUMA topology.
    >> >
    >> > ACPI SRAT tables can expose such a topology which needs to be supported.
    >> >
    >> > Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    >> > Signed-off-by: Ingo Molnar <mingo@elte.hu>
    >> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    >>
    >> Okay, so we have one bdata for node 0 and one for node 1. Does that mean
    >> that both have overlapping pfn ranges?
    >>
    >> [1 ||||| ]
    >> [2 ||||| ]
    >>
    >> Like this? How are the ||||| represented in the bootmem maps of each bdata?
    >
    > Yes.

    Okay. So they share the same PFNs. Now imagine the following scenario:

    node0: 0-2GB, 4-6GB
    node1: 2-4GB, 6-8GB

    /* Marks the range on node0 and node1 */
    free_bootmem(1.5G, 2G);
    /* Frees all bootmem on both nodes */
    free_all_bootmem_node(NODE_DATA(0));
    free_all_bootmem_node(NODE_DATA(1));
    Aren't the same page descriptors send to __free_bootmem_pages() twice?

    Hannes


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