The patch titled
Subject: mm/vmalloc.c: add priority threshold to __purge_vmap_area_lazy()
has been removed from the -mm tree. Its filename was
mm-add-priority-threshold-to-__purge_vmap_area_lazy.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
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 influences the 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.
Using vmalloc test driver in "stress mode", i.e. When all available
test cases are run simultaneously on all online CPUs applying a
pressure on the vmalloc subsystem, my HiKey 960 board runs out of
memory due to the fact that __purge_vmap_area_lazy() logic simply is
not able to free pages in time.
How I run it:
1) You should build your kernel with CONFIG_TEST_VMALLOC=m
2) ./tools/testing/selftests/vm/test_vmalloc.sh stress
During this test "vmap_lazy_nr" pages will go far beyond acceptable
lazy_max_pages() threshold, that will lead to enormous busy list size
and other problems including allocation time and so on.
Link: http://lkml.kernel.org/r/20190124115648.9433-3-urezki@xxxxxxxxx
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
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>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
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
@@ -662,23 +662,27 @@ 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) {
@@ -686,7 +690,9 @@ 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
mm-vmap-keep-track-of-free-blocks-for-vmap-allocation.patch
mm-vmap-keep-track-of-free-blocks-for-vmap-allocation-v3.patch
mm-vmap-keep-track-of-free-blocks-for-vmap-allocation-v4.patch
mm-vmap-add-debug_augment_propagate_check-macro.patch
mm-vmap-add-debug_augment_propagate_check-macro-v4.patch
mm-vmap-add-debug_augment_lowest_match_check-macro.patch
mm-vmap-add-debug_augment_lowest_match_check-macro-v4.patch
