On Wed 26-11-14 14:17:32, David Rientjes wrote:
> Commit b9921ecdee66 ("mm: add a helper function to check may oom
> condition") was added because the gfp criteria for oom killing was
> checked in both the page allocator and memcg.
>
> That was true for about nine months, but then commit 0029e19ebf84 ("mm:
> memcontrol: remove explicit OOM parameter in charge path") removed the
> memcg usecase.
>
> Fold the implementation into its only caller.
I don't care much whether the check is open coded or hidden behind the
helper but I would really appreciate a comment explaining why we care
about these two particular gfp flags. The code is like that since ages
- excavation work would lead us back to 2002 resp. 2003. Let's save
other others people time and do not repeat the same exercise again.
What about a comment like the following?
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> include/linux/oom.h | 5 -----
> mm/page_alloc.c | 2 +-
> 2 files changed, 1 insertion(+), 6 deletions(-)
>
[...]
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2706,7 +2706,7 @@ rebalance:
> * running out of options and have to consider going OOM
> */
> if (!did_some_progress) {
> - if (oom_gfp_allowed(gfp_mask)) {
/*
* Do not attempt to trigger OOM killer for !__GFP_FS
* allocations because it would be premature to kill
* anything just because the reclaim is stuck on
* dirty/writeback pages.
* __GFP_NORETRY allocations might fail and so the OOM
* would be more harmful than useful.
*/
> + if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
> if (oom_killer_disabled)
> goto nopage;
> /* Coredumps can quickly deplete all memory reserves */
--
Michal Hocko
SUSE Labs
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