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author | Paul Jackson <pj@sgi.com> | 2006-05-20 15:00:10 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-05-21 12:59:18 -0700 |
commit | 36be57ffe39e03aab9fbe857f70c7a6a15bd9e08 (patch) | |
tree | 8062e9a9e49fd942fab35e17a2b5afe571a74f63 | |
parent | bdd804f478a0cc74bf7db8e9f9d5fd379d1b31ca (diff) | |
download | linux-36be57ffe39e03aab9fbe857f70c7a6a15bd9e08.tar.gz linux-36be57ffe39e03aab9fbe857f70c7a6a15bd9e08.tar.bz2 linux-36be57ffe39e03aab9fbe857f70c7a6a15bd9e08.zip |
[PATCH] cpuset: update cpuset_zones_allowed comment
Update the kernel/cpuset.c:cpuset_zone_allowed() comment.
The rule for when mm/page_alloc.c should call cpuset_zone_allowed()
was intended to be:
Don't call cpuset_zone_allowed() if you can't sleep, unless you
pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
the code that might scan up ancestor cpusets and sleep.
The explanation of this rule in the comment above cpuset_zone_allowed() was
stale, as a result of a restructuring of some __alloc_pages() code in
November 2005.
Rewrite that comment ...
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r-- | kernel/cpuset.c | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 72248d1b9e3f..57fd88237afc 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2231,19 +2231,25 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs) * So only GFP_KERNEL allocations, if all nodes in the cpuset are * short of memory, might require taking the callback_mutex mutex. * - * The first loop over the zonelist in mm/page_alloc.c:__alloc_pages() - * calls here with __GFP_HARDWALL always set in gfp_mask, enforcing - * hardwall cpusets - no allocation on a node outside the cpuset is - * allowed (unless in interrupt, of course). - * - * The second loop doesn't even call here for GFP_ATOMIC requests - * (if the __alloc_pages() local variable 'wait' is set). That check - * and the checks below have the combined affect in the second loop of - * the __alloc_pages() routine that: + * The first call here from mm/page_alloc:get_page_from_freelist() + * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets, so + * no allocation on a node outside the cpuset is allowed (unless in + * interrupt, of course). + * + * The second pass through get_page_from_freelist() doesn't even call + * here for GFP_ATOMIC calls. For those calls, the __alloc_pages() + * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set + * in alloc_flags. That logic and the checks below have the combined + * affect that: * in_interrupt - any node ok (current task context irrelevant) * GFP_ATOMIC - any node ok * GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok * GFP_USER - only nodes in current tasks mems allowed ok. + * + * Rule: + * Don't call cpuset_zone_allowed() if you can't sleep, unless you + * pass in the __GFP_HARDWALL flag set in gfp_flag, which disables + * the code that might scan up ancestor cpusets and sleep. **/ int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask) |