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libfdt: Add FDT_CREATE_FLAG_NO_NAME_DEDUP flag that trades size for speed

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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@gmail.com>
Message-Id: <20190509094122.834-4-npiggin@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Nicholas Piggin 2019-05-09 19:41:22 +10:00 committed by David Gibson
parent fbb62754ce
commit ce01b21098
4 changed files with 84 additions and 34 deletions
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39
libfdt/fdt_sw.c
View file

@ -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;

8
libfdt/libfdt.h
View file

@ -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

26
tests/run_tests.sh
View file

@ -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
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
tree1_tests sw_tree1.test.dtb
tree1_tests unfinished_tree1.test.dtb
run_test dtbs_equal_ordered test_tree1.dtb sw_tree1.test.dtb
# 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

45
tests/sw_tree1.c
View file

@ -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;