From: Nicholas Piggin <npig...@gmail.com>
Searching for duplicate names scales O(n^2) with the number of names
added to a fdt, which can cause a noticable slowdown with larger device
trees and very slow CPU cores.
Add FDT_CREATE_FLAG_NO_NAME_DEDUP that allow the caller to trade fdt size
for speed in the creation process.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Message-Id: <20190509094122.834-4-npig...@gmail.com>
Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
---
cpukit/dtc/libfdt/fdt_sw.c | 39 ++++++++++++++++++++++++++-------------
cpukit/include/libfdt.h | 8 +++++++-
2 files changed, 33 insertions(+), 14 deletions(-)
diff --git a/cpukit/dtc/libfdt/fdt_sw.c b/cpukit/dtc/libfdt/fdt_sw.c
index ba05868845..e773157d0f 100644
--- a/cpukit/dtc/libfdt/fdt_sw.c
+++ b/cpukit/dtc/libfdt/fdt_sw.c
@@ -284,6 +284,23 @@ int fdt_end_node(void *fdt)
return 0;
}
+static int fdt_add_string_(void *fdt, const char *s)
+{
+ char *strtab = (char *)fdt + fdt_totalsize(fdt);
+ int strtabsize = fdt_size_dt_strings(fdt);
+ int len = strlen(s) + 1;
+ int struct_top, offset;
+
+ offset = -strtabsize - len;
+ struct_top = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt);
+ if (fdt_totalsize(fdt) + offset < struct_top)
+ return 0; /* no more room :( */
+
+ memcpy(strtab + offset, s, len);
+ fdt_set_size_dt_strings(fdt, strtabsize + len);
+ return offset;
+}
+
/* Must only be used to roll back in case of error */
static void fdt_del_last_string_(void *fdt, const char *s)
{
@@ -296,10 +313,8 @@ static void fdt_del_last_string_(void *fdt, const char *s)
static int fdt_find_add_string_(void *fdt, const char *s, int *allocated)
{
char *strtab = (char *)fdt + fdt_totalsize(fdt);
- const char *p;
int strtabsize = fdt_size_dt_strings(fdt);
- int len = strlen(s) + 1;
- int struct_top, offset;
+ const char *p;
*allocated = 0;
@@ -307,17 +322,9 @@ static int fdt_find_add_string_(void *fdt, const char *s,
int *allocated)
if (p)
return p - strtab;
- /* Add it */
*allocated = 1;
- offset = -strtabsize - len;
- struct_top = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt);
- if (fdt_totalsize(fdt) + offset < struct_top)
- return 0; /* no more room :( */
-
- memcpy(strtab + offset, s, len);
- fdt_set_size_dt_strings(fdt, strtabsize + len);
- return offset;
+ return fdt_add_string_(fdt, s);
}
int fdt_property_placeholder(void *fdt, const char *name, int len, void **valp)
@@ -328,7 +335,13 @@ int fdt_property_placeholder(void *fdt, const char *name,
int len, void **valp)
FDT_SW_PROBE_STRUCT(fdt);
- nameoff = fdt_find_add_string_(fdt, name, &allocated);
+ /* String de-duplication can be slow, _NO_NAME_DEDUP skips it */
+ if (sw_flags(fdt) & FDT_CREATE_FLAG_NO_NAME_DEDUP) {
+ allocated = 1;
+ nameoff = fdt_add_string_(fdt, name);
+ } else {
+ nameoff = fdt_find_add_string_(fdt, name, &allocated);
+ }
if (nameoff == 0)
return -FDT_ERR_NOSPACE;
diff --git a/cpukit/include/libfdt.h b/cpukit/include/libfdt.h
index c2dee3eaa6..0684ec22ed 100644
--- a/cpukit/include/libfdt.h
+++ b/cpukit/include/libfdt.h
@@ -1433,7 +1433,13 @@ int fdt_nop_node(void *fdt, int nodeoffset);
/* Sequential write functions */
/**********************************************************************/
-#define FDT_CREATE_FLAGS_ALL 0
+/* fdt_create_with_flags flags */
+#define FDT_CREATE_FLAG_NO_NAME_DEDUP 0x1
+ /* FDT_CREATE_FLAG_NO_NAME_DEDUP: Do not try to de-duplicate property
+ * names in the fdt. This can result in faster creation times, but
+ * a larger fdt. */
+
+#define FDT_CREATE_FLAGS_ALL (FDT_CREATE_FLAG_NO_NAME_DEDUP)
/**
* fdt_create_with_flags - begin creation of a new fdt
--
2.16.4
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