diff options
| author | Feng Tang <feng.tang@intel.com> | 2021-06-30 18:51:00 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-30 20:47:29 -0700 |
| commit | 7858d7bca7fbbbbd5b940d2ec371b2d060b21b84 (patch) | |
| tree | db053bc713903744124e589db402dc410df2296d /include | |
| parent | b26e517a058bd40c790a1d9868c896842f2e4155 (diff) | |
mm/mempolicy: don't handle MPOL_LOCAL like a fake MPOL_PREFERRED policy
MPOL_LOCAL policy has been setup as a real policy, but it is still handled
like a faked POL_PREFERRED policy with one internal MPOL_F_LOCAL flag bit
set, and there are many places having to judge the real 'prefer' or the
'local' policy, which are quite confusing.
In current code, there are 4 cases that MPOL_LOCAL are used:
1. user specifies 'local' policy
2. user specifies 'prefer' policy, but with empty nodemask
3. system 'default' policy is used
4. 'prefer' policy + valid 'preferred' node with MPOL_F_STATIC_NODES
flag set, and when it is 'rebind' to a nodemask which doesn't contains
the 'preferred' node, it will perform as 'local' policy
So make 'local' a real policy instead of a fake 'prefer' one, and kill
MPOL_F_LOCAL bit, which can greatly reduce the confusion for code reading.
For case 4, the logic of mpol_rebind_preferred() is confusing, as Michal
Hocko pointed out:
: I do believe that rebinding preferred policy is just bogus and it should
: be dropped altogether on the ground that a preference is a mere hint from
: userspace where to start the allocation. Unless I am missing something
: cpusets will be always authoritative for the final placement. The
: preferred node just acts as a starting point and it should be really
: preserved when cpusets changes. Otherwise we have a very subtle behavior
: corner cases.
So dump all the tricky transformation between 'prefer' and 'local', and
just record the new nodemask of rebinding.
[feng.tang@intel.com: fix a problem in mpol_set_nodemask(), per Michal Hocko]
Link: https://lkml.kernel.org/r/1622560492-1294-3-git-send-email-feng.tang@intel.com
[feng.tang@intel.com: refine code and comments of mpol_set_nodemask(), per Michal]
Link: https://lkml.kernel.org/r/20210603081807.GE56979@shbuild999.sh.intel.com
Link: https://lkml.kernel.org/r/1622469956-82897-3-git-send-email-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/mempolicy.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h index 4832fd0b5642..19a00bc7fe86 100644 --- a/include/uapi/linux/mempolicy.h +++ b/include/uapi/linux/mempolicy.h @@ -60,7 +60,6 @@ enum { * are never OR'ed into the mode in mempolicy API arguments. */ #define MPOL_F_SHARED (1 << 0) /* identify shared policies */ -#define MPOL_F_LOCAL (1 << 1) /* preferred local allocation */ #define MPOL_F_MOF (1 << 3) /* this policy wants migrate on fault */ #define MPOL_F_MORON (1 << 4) /* Migrate On protnone Reference On Node */ |