* [PATCH v2 1/2] of: reserved_mem: Try to keep range allocations contiguous
2023-06-14 19:20 [PATCH v2 0/2] of: reserved_mem: Improve range allocations Stephan Gerhold
@ 2023-06-14 19:20 ` Stephan Gerhold
2023-06-20 15:34 ` Rob Herring
2023-06-14 19:20 ` [PATCH v2 2/2] of: reserved_mem: Use stable allocation order Stephan Gerhold
1 sibling, 1 reply; 5+ messages in thread
From: Stephan Gerhold @ 2023-06-14 19:20 UTC (permalink / raw)
To: Rob Herring, Krzysztof Kozlowski, Conor Dooley, Frank Rowand
Cc: Andy Gross, Bjorn Andersson, Konrad Dybcio, devicetree,
devicetree-spec, linux-kernel, linux-arm-msm, Stephan Gerhold
Right now dynamic reserved memory regions are allocated either
bottom-up or top-down, depending on the memblock setting of the
architecture. This is fine when the address is arbitrary. However,
when using "alloc-ranges" the regions are often placed somewhere
in the middle of (free) RAM, even if the range starts or ends next
to another (static) reservation.
Try to detect this situation, and choose explicitly between bottom-up
or top-down to allocate the memory close to the other reservations:
1. If the "alloc-range" starts at the end or inside an existing
reservation, use bottom-up.
2. If the "alloc-range" ends at the start or inside an existing
reservation, use top-down.
3. If both or none is the case, keep the current
(architecture-specific) behavior.
There are plenty of edge cases where only a more complex algorithm
would help, but even this simple approach helps in many cases to keep
the reserved memory (and therefore also the free memory) contiguous.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
---
drivers/of/of_reserved_mem.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 53 insertions(+), 2 deletions(-)
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 948efa9f99e3..7f892c3dcc63 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -77,6 +77,57 @@ void __init fdt_reserved_mem_save_node(unsigned long node, const char *uname,
return;
}
+/*
+ * __reserved_mem_alloc_in_range() - allocate reserved memory described with
+ * 'alloc-ranges'. Choose bottom-up/top-down depending on nearby existing
+ * reserved regions to keep the reserved memory contiguous if possible.
+ */
+static int __init __reserved_mem_alloc_in_range(phys_addr_t size,
+ phys_addr_t align, phys_addr_t start, phys_addr_t end, bool nomap,
+ phys_addr_t *res_base)
+{
+ bool prev_bottom_up = memblock_bottom_up();
+ bool bottom_up = false, top_down = false;
+ int ret, i;
+
+ for (i = 0; i < reserved_mem_count; i++) {
+ struct reserved_mem *rmem = &reserved_mem[i];
+
+ /* Skip regions that were not reserved yet */
+ if (rmem->size == 0)
+ continue;
+
+ /*
+ * If range starts next to an existing reservation, use bottom-up:
+ * |....RRRR................RRRRRRRR..............|
+ * --RRRR------
+ */
+ if (start >= rmem->base && start <= (rmem->base + rmem->size))
+ bottom_up = true;
+
+ /*
+ * If range ends next to an existing reservation, use top-down:
+ * |....RRRR................RRRRRRRR..............|
+ * -------RRRR-----
+ */
+ if (end >= rmem->base && end <= (rmem->base + rmem->size))
+ top_down = true;
+ }
+
+ /* Change setting only if either bottom-up or top-down was selected */
+ if (bottom_up != top_down)
+ memblock_set_bottom_up(bottom_up);
+
+ ret = early_init_dt_alloc_reserved_memory_arch(size, align,
+ start, end, nomap, res_base);
+
+ /* Restore old setting if needed */
+ if (bottom_up != top_down)
+ memblock_set_bottom_up(prev_bottom_up);
+
+ return ret;
+}
+
/*
* __reserved_mem_alloc_size() - allocate reserved memory described by
* 'size', 'alignment' and 'alloc-ranges' properties.
@@ -137,8 +188,8 @@ static int __init __reserved_mem_alloc_size(unsigned long node,
end = start + dt_mem_next_cell(dt_root_size_cells,
&prop);
- ret = early_init_dt_alloc_reserved_memory_arch(size,
- align, start, end, nomap, &base);
+ ret = __reserved_mem_alloc_in_range(size, align,
+ start, end, nomap, &base);
if (ret == 0) {
pr_debug("allocated memory for '%s' node: base %pa, size %lu MiB\n",
uname, &base,
--
2.40.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v2 2/2] of: reserved_mem: Use stable allocation order
2023-06-14 19:20 [PATCH v2 0/2] of: reserved_mem: Improve range allocations Stephan Gerhold
2023-06-14 19:20 ` [PATCH v2 1/2] of: reserved_mem: Try to keep range allocations contiguous Stephan Gerhold
@ 2023-06-14 19:20 ` Stephan Gerhold
2023-06-20 15:35 ` Rob Herring
1 sibling, 1 reply; 5+ messages in thread
From: Stephan Gerhold @ 2023-06-14 19:20 UTC (permalink / raw)
To: Rob Herring, Krzysztof Kozlowski, Conor Dooley, Frank Rowand
Cc: Andy Gross, Bjorn Andersson, Konrad Dybcio, devicetree,
devicetree-spec, linux-kernel, linux-arm-msm, Stephan Gerhold
sort() in Linux is based on heapsort which is not a stable sort
algorithm - equal elements are being reordered. For reserved memory in
the device tree this happens mainly for dynamic allocations: They do not
have an address to sort with, so they are reordered somewhat randomly
when adding/removing other unrelated reserved memory nodes.
Functionally this is not a big problem, but it's confusing during
development when all the addresses change after adding unrelated
reserved memory nodes.
Make the order stable by sorting dynamic allocations according to
the node order in the device tree. Static allocations are not affected
by this because they are still sorted by their (fixed) address.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
---
drivers/of/of_reserved_mem.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 7f892c3dcc63..7ec94cfcbddb 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -268,6 +268,11 @@ static int __init __rmem_cmp(const void *a, const void *b)
if (ra->size > rb->size)
return 1;
+ if (ra->fdt_node < rb->fdt_node)
+ return -1;
+ if (ra->fdt_node > rb->fdt_node)
+ return 1;
+
return 0;
}
--
2.40.1
^ permalink raw reply related [flat|nested] 5+ messages in thread