The patch titled
Subject: mm/vmalloc.c: add priority threshold to __purge_vmap_area_lazy()
has been added to the -mm tree. Its filename is
mm-add-priority-threshold-to-__purge_vmap_area_lazy.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-priority-threshold-to-__purge_vmap_area_lazy.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-priority-threshold-to-__purge_vmap_area_lazy.patch
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------------------------------------------------------
From: "Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx>
Subject: mm/vmalloc.c: add priority threshold to __purge_vmap_area_lazy()
763b218ddfaf ("mm: add preempt points into __purge_vmap_area_lazy()")
introduced some preempt points, one of those is making an allocation more
prioritized over lazy free of vmap areas.
Prioritizing an allocation over freeing does not work well all the time,
i.e. it should be rather a compromise.
1) Number of lazy pages directly influence on busy list length thus on
operations like: allocation, lookup, unmap, remove, etc.
2) Under heavy stress of vmalloc subsystem i run into a situation when
memory usage gets increased hitting out_of_memory -> panic state due to
completely blocking of logic that frees vmap areas in the
__purge_vmap_area_lazy() function.
Establish a threshold passing which the freeing is prioritized back over
allocation creating a balance between each other.
Link: http://lkml.kernel.org/r/20190124115648.9433-3-urezki@xxxxxxxxx
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Thomas Garnier <thgarnie@xxxxxxxxxx>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
--- a/mm/vmalloc.c~mm-add-priority-threshold-to-__purge_vmap_area_lazy
+++ a/mm/vmalloc.c
@@ -661,23 +661,27 @@ static bool __purge_vmap_area_lazy(unsig
struct llist_node *valist;
struct vmap_area *va;
struct vmap_area *n_va;
- bool do_free = false;
+ int resched_threshold;
lockdep_assert_held(&vmap_purge_lock);
valist = llist_del_all(&vmap_purge_list);
+ if (unlikely(valist == NULL))
+ return false;
+
+ /*
+ * TODO: to calculate a flush range without looping.
+ * The list can be up to lazy_max_pages() elements.
+ */
llist_for_each_entry(va, valist, purge_list) {
if (va->va_start < start)
start = va->va_start;
if (va->va_end > end)
end = va->va_end;
- do_free = true;
}
- if (!do_free)
- return false;
-
flush_tlb_kernel_range(start, end);
+ resched_threshold = (int) lazy_max_pages() << 1;
spin_lock(&vmap_area_lock);
llist_for_each_entry_safe(va, n_va, valist, purge_list) {
@@ -685,7 +689,9 @@ static bool __purge_vmap_area_lazy(unsig
__free_vmap_area(va);
atomic_sub(nr, &vmap_lazy_nr);
- cond_resched_lock(&vmap_area_lock);
+
+ if (atomic_read(&vmap_lazy_nr) < resched_threshold)
+ cond_resched_lock(&vmap_area_lock);
}
spin_unlock(&vmap_area_lock);
return true;
_
Patches currently in -mm which might be from urezki@xxxxxxxxx are
vmalloc-export-__vmalloc_node_range-for-config_test_vmalloc_module.patch
vmalloc-add-test-driver-to-analyse-vmalloc-allocator.patch
vmalloc-add-test-driver-to-analyse-vmalloc-allocator-fix.patch
selftests-vm-add-script-helper-for-config_test_vmalloc_module.patch
mm-vmalloc-fix-kernel-bug-at-mm-vmallocc-512.patch
mm-add-priority-threshold-to-__purge_vmap_area_lazy.patch
