lkml.org 
[lkml]   [2008]   [Mar]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3 (RFC)](memory hotplug) align maps for easy removing
On Fri, Mar 14, 2008 at 7:44 AM, Yasunori Goto <y-goto@jp.fujitsu.com> wrote:
>
> To free memmap and usemap easier, this patch aligns these maps to page size.
>
> I know usemap size is too small to align page size.
> It will be waste of area. So, there may be better way than this.
>
> Followings are pros. and cons with other my ideas.
> But I'm not sure which is better way.
>
> a) Packing many section's usemap on one page. Count how many sections use
> it in page_count.
> Pros.
> - Avoid waisting area.
> Cons.
> - This usemap's page will be hard(or impossible) to remove due to
> dependency.
> It should be allocated on un-movable zone/node.
> (I'm not sure it's impact of performance.)
> - Nodes' structures may have to be packed like usemap???
>
> b) Pack memmap and usemap in one allocation.
> Pros.
> - May avoid wasting area if its size is suitable.
> Cons.
> - If size is not suitable, it will be same as this patch.
> - This way is not good for VMEMMAP_SPARSEMEM.
> At least, it is reverse way against Yinghai-san's fix.
>
> c) This way.
> Pros.
> - Very easy to remove.
> Cons.
> - Waist of area.
>
> Any other idea is welcome.
>
>
> Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
>
> ---
> mm/sparse.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> Index: current/mm/sparse.c
> ===================================================================
> --- current.orig/mm/sparse.c 2008-03-11 20:15:41.000000000 +0900
> +++ current/mm/sparse.c 2008-03-11 20:58:18.000000000 +0900
> @@ -244,7 +244,8 @@
> struct mem_section *ms = __nr_to_section(pnum);
> int nid = sparse_early_nid(ms);
>
> - usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
> + usemap = alloc_bootmem_pages_node(NODE_DATA(nid),
> + PAGE_ALIGN(usemap_size()));

if we allocate usemap continuously,
old way could make different usermap share one page. usermap size is
only about 24bytes. align to 128bytes ( the SMP cache lines)

sparse_early_usemap_alloc: usemap = ffff810024e00000 size = 24
sparse_early_usemap_alloc: usemap = ffff810024e00080 size = 24
sparse_early_usemap_alloc: usemap = ffff810024e00100 size = 24
sparse_early_usemap_alloc: usemap = ffff810024e00180 size = 24


YH


\
 
 \ /
  Last update: 2008-03-14 17:29    [W:0.067 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site