lkml.org 
[lkml]   [2010]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] Make is_mem_section_removable more conformable with offlining code
    Hi Michal,

    It helps to explain in changelog/code

    - in what situation a ZONE_MOVABLE will contain !MIGRATE_MOVABLE
    pages? And why the MIGRATE_MOVABLE test is still necessary given the
    ZONE_MOVABLE check?

    - why do you think free pages are not removeable? Simply to cater for
    the set_migratetype_isolate() logic, or there are more fundamental
    reasons?

    Thanks,
    Fengguang

    On Fri, Aug 20, 2010 at 04:14:00PM +0200, Michal Hocko wrote:
    > Hi,
    > what do you think about the patch below?
    >
    > >From b983695b92b5be58f31c719fada1d3245f7b6768 Mon Sep 17 00:00:00 2001
    > From: Michal Hocko <mhocko@suse.cz>
    > Date: Fri, 20 Aug 2010 15:39:16 +0200
    > Subject: [PATCH] Make is_mem_section_removable more conformable with offlining code
    >
    > Currently is_mem_section_removable checks whether each pageblock from
    > the given pfn range is of MIGRATE_MOVABLE type or if it is free. If both
    > are false then the range is considered non removable.
    >
    > On the other hand, offlining code (more specifically
    > set_migratetype_isolate) doesn't care whether a page is free and instead
    > it just checks the migrate type of the page and whether the page's zone
    > is movable.
    >
    > This can lead into a situation when a node is marked as removable even
    > though all pages are neither MIGRATE_MOVABLE nor the zone is
    > ZONE_MOVABLE.
    >
    > Also we can mark a node as not removable just because a pageblock is
    > MIGRATE_RESERVE and not free (and this situation is much more probable).
    > ---
    > mm/memory_hotplug.c | 6 +++---
    > 1 files changed, 3 insertions(+), 3 deletions(-)
    >
    > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
    > index a4cfcdc..da20568 100644
    > --- a/mm/memory_hotplug.c
    > +++ b/mm/memory_hotplug.c
    > @@ -611,10 +611,10 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
    > type = get_pageblock_migratetype(page);
    >
    > /*
    > - * A pageblock containing MOVABLE or free pages is considered
    > - * removable
    > + * A pageblock containing MOVABLE or page from movable
    > + * zone are considered removable
    > */
    > - if (type != MIGRATE_MOVABLE && !pageblock_free(page))
    > + if (type != MIGRATE_MOVABLE && zone_idx(page) != ZONE_MOVABLE)
    > return 0;
    >
    > /*
    > --
    > 1.7.1
    >
    >
    > --
    > Michal Hocko
    > L3 team
    > SUSE LINUX s.r.o.
    > Lihovarska 1060/12
    > 190 00 Praha 9
    > Czech Republic
    >
    > --
    > To unsubscribe, send a message with 'unsubscribe linux-mm' in
    > the body to majordomo@kvack.org. For more info on Linux MM,
    > see: http://www.linux-mm.org/ .
    > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>


    \
     
     \ /
      Last update: 2010-08-22 02:45    [W:0.044 / U:181.148 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site