The patch titled
Subject: mm/vmscan: drop unneeded assignment in kswapd()
has been added to the -mm tree. Its filename is
mm-vmscan-drop-unneeded-assignment-in-kswapd.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscan-drop-unneeded-assignment-in-kswapd.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-drop-unneeded-assignment-in-kswapd.patch
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------------------------------------------------------
From: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Subject: mm/vmscan: drop unneeded assignment in kswapd()
The refactoring to kswapd() in commit e716f2eb24de ("mm, vmscan: prevent
kswapd sleeping prematurely due to mismatched classzone_idx") turned an
assignment to reclaim_order into a dead store, as in all further paths,
reclaim_order will be assigned again before it is used.
make clang-analyzer on x86_64 tinyconfig caught my attention with:
mm/vmscan.c: warning: Although the value stored to 'reclaim_order' is
used in the enclosing expression, the value is never actually read from
'reclaim_order' [clang-analyzer-deadcode.DeadStores]
Compilers will detect this unneeded assignment and optimize this anyway.
So, the resulting binary is identical before and after this change.
Simplify the code and remove unneeded assignment to make clang-analyzer
happy.
No functional change. No change in binary code.
Link: https://lkml.kernel.org/r/20201004125827.17679-1-lukas.bulwahn@xxxxxxxxx
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Nathan Chancellor <natechancellor@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmscan.c~mm-vmscan-drop-unneeded-assignment-in-kswapd
+++ a/mm/vmscan.c
@@ -3898,7 +3898,7 @@ kswapd_try_sleep:
highest_zoneidx);
/* Read the new order and highest_zoneidx */
- alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order);
+ alloc_order = READ_ONCE(pgdat->kswapd_order);
highest_zoneidx = kswapd_highest_zoneidx(pgdat,
highest_zoneidx);
WRITE_ONCE(pgdat->kswapd_order, 0);
_
Patches currently in -mm which might be from lukas.bulwahn@xxxxxxxxx are
mm-vmscan-drop-unneeded-assignment-in-kswapd.patch
