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 <npiggin@xxxxxxxxx>
---
libfdt/fdt_sw.c | 39 ++++++++++++++++++++++++++-------------
libfdt/libfdt.h | 8 +++++++-
tests/run_tests.sh | 28 +++++++++++++++-------------
tests/sw_tree1.c | 45 +++++++++++++++++++++++++++++++++++++--------
4 files changed, 85 insertions(+), 35 deletions(-)
diff --git a/libfdt/fdt_sw.c b/libfdt/fdt_sw.c
index ba05868..e773157 100644
--- a/libfdt/fdt_sw.c
+++ b/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/libfdt/libfdt.h b/libfdt/libfdt.h
index c2dee3e..0684ec2 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/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
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index d350c3d..07c3489 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -354,19 +354,21 @@ libfdt_tests () {
run_dtc_test -I dts -O dtb -o stringlist.test.dtb stringlist.dts
run_test stringlist stringlist.test.dtb
- # Sequential write tests
- run_test sw_tree1
- tree1_tests sw_tree1.test.dtb
- tree1_tests unfinished_tree1.test.dtb
- run_test dtbs_equal_ordered test_tree1.dtb sw_tree1.test.dtb
- run_test sw_states
-
- # Resizing tests
- for mode in resize realloc newalloc; do
- run_test sw_tree1 $mode
- tree1_tests sw_tree1.test.dtb
- tree1_tests unfinished_tree1.test.dtb
- run_test dtbs_equal_ordered test_tree1.dtb sw_tree1.test.dtb
+ for flags in default no_name_dedup; do
+ # Sequential write tests
+ run_test sw_tree1 fixed $flags
+ tree1_tests sw_tree1.test.dtb
+ tree1_tests unfinished_tree1.test.dtb
+ run_test dtbs_equal_ordered test_tree1.dtb sw_tree1.test.dtb
+ run_test sw_states
+
+ # Resizing tests
+ for mode in resize realloc newalloc; do
+ run_test sw_tree1 $mode $flags
+ tree1_tests sw_tree1.test.dtb
+ tree1_tests unfinished_tree1.test.dtb
+ run_test dtbs_equal_ordered test_tree1.dtb sw_tree1.test.dtb
+ done
done
# fdt_move tests
diff --git a/tests/sw_tree1.c b/tests/sw_tree1.c
index 2a67c12..08b39b3 100644
--- a/tests/sw_tree1.c
+++ b/tests/sw_tree1.c
@@ -114,14 +114,19 @@ int main(int argc, char *argv[])
void *place;
const char place_str[] = "this is a placeholder string\0string2";
int place_len = sizeof(place_str);
+ int create_flags;
test_init(argc, argv);
- if (argc == 1) {
- alloc_mode = FIXED;
- size = SPACE;
- } else if (argc == 2) {
- if (streq(argv[1], "resize")) {
+ alloc_mode = FIXED;
+ size = SPACE;
+ create_flags = 0;
+
+ if (argc == 2 || argc == 3) {
+ if (streq(argv[1], "fixed")) {
+ alloc_mode = FIXED;
+ size = SPACE;
+ } else if (streq(argv[1], "resize")) {
alloc_mode = REALLOC;
size = 0;
} else if (streq(argv[1], "realloc")) {
@@ -140,12 +145,36 @@ int main(int argc, char *argv[])
CONFIG("Bad allocation mode \"%s\" specified",
argv[1]);
}
- } else {
- CONFIG("sw_tree1 <dtb file> [<allocation mode>]");
+ }
+ if (argc == 3) {
+ char *str = argv[2], *saveptr, *tok;
+ bool default_flag = false;
+
+ while ((tok = strtok_r(str, ",", &saveptr)) != NULL) {
+ str = NULL;
+ if (streq(tok, "default")) {
+ default_flag = true;
+ } else if (streq(tok, "no_name_dedup")) {
+ create_flags |= FDT_CREATE_FLAG_NO_NAME_DEDUP;
+ } else if (streq(tok, "bad")) {
+ create_flags |= 0xffffffff;
+ } else {
+ CONFIG("Bad creation flags \"%s\" specified",
+ argv[2]);
+ }
+ }
+
+ if (default_flag && create_flags != 0)
+ CONFIG("Bad creation flags \"%s\" specified",
+ argv[2]);
+ }
+
+ if (argc > 3) {
+ CONFIG("sw_tree1 [<allocation mode>] [<create flags>]");
}
fdt = xmalloc(size);
- CHECK(fdt_create(fdt, size));
+ CHECK(fdt_create_with_flags(fdt, size, create_flags));
created = true;
--
2.20.1
