The patch titled
Subject: resource: introduce resource cache
has been added to the -mm tree. Its filename is
resource-introduce-resource-cache.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/resource-introduce-resource-cache.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/resource-introduce-resource-cache.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Nadav Amit <namit@xxxxxxxxxx>
Subject: resource: introduce resource cache
For efficient search of resources, as needed to determine the memory type
for dax page-faults, introduce a cache of the most recently used top-level
resource. Caching the top-level should be safe as ranges in that level do
not overlap (unlike those of lower levels).
Keep the cache per-cpu to avoid possible contention. Whenever a resource
is added, removed or changed, invalidate all the resources. The
invalidation takes place when the resource_lock is taken for write,
preventing possible races.
This patch provides relatively small performance improvements over the
previous patch (~0.5% on sysbench), but can benefit systems with many
resources.
Link: http://lkml.kernel.org/r/20190613045903.4922-4-namit@xxxxxxxxxx
Signed-off-by: Nadav Amit <namit@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/resource.c | 51 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)
--- a/kernel/resource.c~resource-introduce-resource-cache
+++ a/kernel/resource.c
@@ -54,6 +54,12 @@ struct resource_constraint {
static DEFINE_RWLOCK(resource_lock);
/*
+ * Cache of the top-level resource that was most recently use by
+ * find_next_iomem_res().
+ */
+static DEFINE_PER_CPU(struct resource *, resource_cache);
+
+/*
* For memory hotplug, there is no way to free resource entries allocated
* by boot mem after the system is up. So for reusing the resource entry
* we need to remember the resource.
@@ -262,9 +268,20 @@ static void __release_child_resources(st
}
}
+static void invalidate_resource_cache(void)
+{
+ int cpu;
+
+ lockdep_assert_held_exclusive(&resource_lock);
+
+ for_each_possible_cpu(cpu)
+ per_cpu(resource_cache, cpu) = NULL;
+}
+
void release_child_resources(struct resource *r)
{
write_lock(&resource_lock);
+ invalidate_resource_cache();
__release_child_resources(r);
write_unlock(&resource_lock);
}
@@ -281,6 +298,7 @@ struct resource *request_resource_confli
struct resource *conflict;
write_lock(&resource_lock);
+ invalidate_resource_cache();
conflict = __request_resource(root, new);
write_unlock(&resource_lock);
return conflict;
@@ -312,6 +330,7 @@ int release_resource(struct resource *ol
int retval;
write_lock(&resource_lock);
+ invalidate_resource_cache();
retval = __release_resource(old, true);
write_unlock(&resource_lock);
return retval;
@@ -343,7 +362,7 @@ static int find_next_iomem_res(resource_
bool first_lvl, struct resource *res)
{
bool siblings_only = true;
- struct resource *p;
+ struct resource *p, *res_first_lvl;
if (!res)
return -EINVAL;
@@ -353,7 +372,15 @@ static int find_next_iomem_res(resource_
read_lock(&resource_lock);
- for (p = iomem_resource.child; p; p = next_resource(p, siblings_only)) {
+ /*
+ * If our cached entry preceded or matches the range that we are looking
+ * for, start with it. Otherwise, start from the beginning.
+ */
+ p = res_first_lvl = this_cpu_read(resource_cache);
+ if (!p || start < p->start)
+ p = iomem_resource.child;
+
+ for (; p; p = next_resource(p, siblings_only)) {
/* If we passed the resource we are looking for, stop */
if (p->start > end) {
p = NULL;
@@ -364,6 +391,10 @@ static int find_next_iomem_res(resource_
if (p->end < start)
continue;
+ /* We only cache the first level for correctness */
+ if (p->parent == &iomem_resource)
+ res_first_lvl = p;
+
/*
* Now that we found a range that matches what we look for,
* check the flags and the descriptor. If we were not asked to
@@ -386,6 +417,9 @@ static int find_next_iomem_res(resource_
res->end = min(end, p->end);
res->flags = p->flags;
res->desc = p->desc;
+
+ /* Update the cache */
+ this_cpu_write(resource_cache, res_first_lvl);
}
read_unlock(&resource_lock);
@@ -674,6 +708,7 @@ static int reallocate_resource(struct re
struct resource *conflict;
write_lock(&resource_lock);
+ invalidate_resource_cache();
if ((err = __find_resource(root, old, &new, newsize, constraint)))
goto out;
@@ -744,6 +779,7 @@ int allocate_resource(struct resource *r
}
write_lock(&resource_lock);
+ invalidate_resource_cache();
err = find_resource(root, new, size, &constraint);
if (err >= 0 && __request_resource(root, new))
err = -EBUSY;
@@ -848,6 +884,7 @@ struct resource *insert_resource_conflic
struct resource *conflict;
write_lock(&resource_lock);
+ invalidate_resource_cache();
conflict = __insert_resource(parent, new);
write_unlock(&resource_lock);
return conflict;
@@ -886,6 +923,7 @@ void insert_resource_expand_to_fit(struc
return;
write_lock(&resource_lock);
+ invalidate_resource_cache();
for (;;) {
struct resource *conflict;
@@ -926,6 +964,7 @@ int remove_resource(struct resource *old
int retval;
write_lock(&resource_lock);
+ invalidate_resource_cache();
retval = __release_resource(old, false);
write_unlock(&resource_lock);
return retval;
@@ -985,6 +1024,7 @@ int adjust_resource(struct resource *res
int result;
write_lock(&resource_lock);
+ invalidate_resource_cache();
result = __adjust_resource(res, start, size);
write_unlock(&resource_lock);
return result;
@@ -1059,6 +1099,8 @@ reserve_region_with_split(struct resourc
int abort = 0;
write_lock(&resource_lock);
+ invalidate_resource_cache();
+
if (root->start > start || root->end < end) {
pr_err("requested range [0x%llx-0x%llx] not in root %pr\n",
(unsigned long long)start, (unsigned long long)end,
@@ -1135,6 +1177,7 @@ struct resource * __request_region(struc
res->end = start + n - 1;
write_lock(&resource_lock);
+ invalidate_resource_cache();
for (;;) {
struct resource *conflict;
@@ -1168,6 +1211,7 @@ struct resource * __request_region(struc
schedule();
remove_wait_queue(&muxed_resource_wait, &wait);
write_lock(&resource_lock);
+ invalidate_resource_cache();
continue;
}
/* Uhhuh, that didn't work out.. */
@@ -1198,6 +1242,7 @@ void __release_region(struct resource *p
end = start + n - 1;
write_lock(&resource_lock);
+ invalidate_resource_cache();
for (;;) {
struct resource *res = *p;
@@ -1211,6 +1256,7 @@ void __release_region(struct resource *p
}
if (res->start != start || res->end != end)
break;
+
*p = res->sibling;
write_unlock(&resource_lock);
if (res->flags & IORESOURCE_MUXED)
@@ -1268,6 +1314,7 @@ int release_mem_region_adjustable(struct
p = &parent->child;
write_lock(&resource_lock);
+ invalidate_resource_cache();
while ((res = *p)) {
if (res->start >= end)
_
Patches currently in -mm which might be from namit@xxxxxxxxxx are
resource-fix-locking-in-find_next_iomem_res.patch
resource-avoid-unnecessary-lookups-in-find_next_iomem_res.patch
resource-introduce-resource-cache.patch
