The patch titled
Subject: mm: remove misleading 'unlikely' hint in vms_gather_munmap_vmas()
has been added to the -mm mm-unstable branch. Its filename is
mm-remove-misleading-unlikely-hint-in-vms_gather_munmap_vmas.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-remove-misleading-unlikely-hint-in-vms_gather_munmap_vmas.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Breno Leitao <leitao@xxxxxxxxxx>
Subject: mm: remove misleading 'unlikely' hint in vms_gather_munmap_vmas()
Date: Fri, 4 Oct 2024 09:48:31 -0700
Performance analysis using branch annotation on a fleet of 200 hosts
running web servers revealed that the 'unlikely' hint in
vms_gather_munmap_vmas() was 100% consistently incorrect. In all observed
cases, the branch behavior contradicted the hint.
Remove the 'unlikely' qualifier from the condition checking 'vms->uf'. By
doing so, we allow the compiler to make optimization decisions based on
its own heuristics and profiling data, rather than relying on a static
hint that has proven to be inaccurate in real-world scenarios.
Link: https://lkml.kernel.org/r/20241004164832.218681-1-leitao@xxxxxxxxxx
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vma.c~mm-remove-misleading-unlikely-hint-in-vms_gather_munmap_vmas
+++ a/mm/vma.c
@@ -1250,7 +1250,7 @@ int vms_gather_munmap_vmas(struct vma_mu
else if (is_data_mapping(next->vm_flags))
vms->data_vm += nrpages;
- if (unlikely(vms->uf)) {
+ if (vms->uf) {
/*
* If userfaultfd_unmap_prep returns an error the vmas
* will remain split, but userland will get a
_
Patches currently in -mm which might be from leitao@xxxxxxxxxx are
mm-remove-misleading-unlikely-hint-in-vms_gather_munmap_vmas.patch
scripts-decode_stacktracesh-remove-trailing-space.patch
