[compiler-rt] r181924 - Try to improve performance by using a read/write buffer instead of I/O.
Reid Kleckner
rnk at google.com
Thu May 16 09:22:37 PDT 2013
On Wed, May 15, 2013 at 5:31 PM, Bill Wendling <isanbard at gmail.com> wrote:
> Author: void
> Date: Wed May 15 16:31:22 2013
> New Revision: 181924
>
> URL: http://llvm.org/viewvc/llvm-project?rev=181924&view=rev
> Log:
> Try to improve performance by using a read/write buffer instead of I/O.
>
> The calls to fwrite/fread can be very expensive. GCC avoids this by using a
> buffer to read and write from the file, thus limiting the number of
> fwrite/fread
> calls.
>
> <rdar://problem/13466086>
>
> Modified:
> compiler-rt/trunk/SDKs/darwin/usr/include/stdio.h
> compiler-rt/trunk/SDKs/darwin/usr/include/string.h
> compiler-rt/trunk/SDKs/linux/usr/include/stdio.h
> compiler-rt/trunk/SDKs/linux/usr/include/string.h
> compiler-rt/trunk/lib/profile/GCDAProfiling.c
>
> Modified: compiler-rt/trunk/SDKs/darwin/usr/include/stdio.h
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/SDKs/darwin/usr/include/stdio.h?rev=181924&r1=181923&r2=181924&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/SDKs/darwin/usr/include/stdio.h (original)
> +++ compiler-rt/trunk/SDKs/darwin/usr/include/stdio.h Wed May 15 16:31:22
> 2013
> @@ -74,6 +74,7 @@ size_t fwrite(const void * __restrict, s
> size_t fread(void * __restrict, size_t, size_t, FILE * __restrict);
> long ftell(FILE *);
> int fseek(FILE *, long, int);
> +void setbuf(FILE * __restrict, char * __restrict);
>
> int snprintf(char * __restrict, size_t, const char * __restrict, ...);
>
>
> Modified: compiler-rt/trunk/SDKs/darwin/usr/include/string.h
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/SDKs/darwin/usr/include/string.h?rev=181924&r1=181923&r2=181924&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/SDKs/darwin/usr/include/string.h (original)
> +++ compiler-rt/trunk/SDKs/darwin/usr/include/string.h Wed May 15 16:31:22
> 2013
> @@ -21,6 +21,7 @@ typedef __SIZE_TYPE__ size_t;
>
> int memcmp(const void *, const void *, size_t);
> void *memcpy(void *, const void *, size_t);
> +void *memset(void *, int, size_t);
> char *strcat(char *, const char *);
> char *strcpy(char *, const char *);
> char *strdup(const char *);
>
> Modified: compiler-rt/trunk/SDKs/linux/usr/include/stdio.h
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/SDKs/linux/usr/include/stdio.h?rev=181924&r1=181923&r2=181924&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/SDKs/linux/usr/include/stdio.h (original)
> +++ compiler-rt/trunk/SDKs/linux/usr/include/stdio.h Wed May 15 16:31:22
> 2013
> @@ -38,5 +38,6 @@ extern size_t fwrite(const void * restri
> extern size_t fread(void * restrict, size_t, size_t, FILE * restrict);
> extern long ftell(FILE *);
> extern int fseek(FILE *, long, int);
> +extern void setbuf(FILE * restrict, char * restrict);
>
> #endif /* __STDIO_H__ */
>
> Modified: compiler-rt/trunk/SDKs/linux/usr/include/string.h
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/SDKs/linux/usr/include/string.h?rev=181924&r1=181923&r2=181924&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/SDKs/linux/usr/include/string.h (original)
> +++ compiler-rt/trunk/SDKs/linux/usr/include/string.h Wed May 15 16:31:22
> 2013
> @@ -21,6 +21,7 @@ typedef __SIZE_TYPE__ size_t;
>
> int memcmp(const void *, const void *, size_t);
> void *memcpy(void *, const void *, size_t);
> +void *memset(void *, int, size_t);
> char *strcat(char *, const char *);
> char *strcpy(char *, const char *);
> char *strdup(const char *);
>
> Modified: compiler-rt/trunk/lib/profile/GCDAProfiling.c
> URL:
> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/profile/GCDAProfiling.c?rev=181924&r1=181923&r2=181924&view=diff
>
> ==============================================================================
> --- compiler-rt/trunk/lib/profile/GCDAProfiling.c (original)
> +++ compiler-rt/trunk/lib/profile/GCDAProfiling.c Wed May 15 16:31:22 2013
> @@ -48,6 +48,15 @@ typedef unsigned int uint64_t;
> static FILE *output_file = NULL;
>
> /*
> + * Buffer that we write things into.
> + */
> +#define WRITE_BUFFER_SIZE (1 << 12)
> +static char write_buffer[WRITE_BUFFER_SIZE];
> +static int64_t cur_file_pos = 0;
> +static uint32_t cur_offset = 0;
> +static int new_file = 0;
> +
> +/*
> * A list of functions to write out the data.
> */
> typedef void (*writeout_fn)();
> @@ -57,8 +66,8 @@ struct writeout_fn_node {
> struct writeout_fn_node *next;
> };
>
> -struct writeout_fn_node *writeout_fn_head = NULL;
> -struct writeout_fn_node *writeout_fn_tail = NULL;
> +static struct writeout_fn_node *writeout_fn_head = NULL;
> +static struct writeout_fn_node *writeout_fn_tail = NULL;
>
> /*
> * A list of flush functions that our __gcov_flush() function should
> call.
> @@ -70,18 +79,41 @@ struct flush_fn_node {
> struct flush_fn_node *next;
> };
>
> -struct flush_fn_node *flush_fn_head = NULL;
> -struct flush_fn_node *flush_fn_tail = NULL;
> +static struct flush_fn_node *flush_fn_head = NULL;
> +static struct flush_fn_node *flush_fn_tail = NULL;
> +
> +static void flush_buffer() {
> + /* Flush the buffer to file. */
> + fwrite(write_buffer, cur_offset, 1, output_file);
> +
> + if (new_file) {
> + cur_offset = 0;
> + return;
> + }
> +
> + /* Read in more of the file. */
> + fread(write_buffer,1, WRITE_BUFFER_SIZE, output_file);
> + fseek(output_file, cur_file_pos, SEEK_SET);
>
> -static void write_int32(uint32_t i) {
> - fwrite(&i, 4, 1, output_file);
> + cur_offset = 0;
> }
>
> -static uint64_t write_from_buffer(uint64_t *buffer, size_t size) {
> - if (fwrite(buffer, 8, size, output_file) != size)
> - return (uint64_t)-1;
> +static void write_bytes(const char *s, size_t len) {
> + if (cur_offset + len > WRITE_BUFFER_SIZE)
> + flush_buffer();
>
Can len be > WRITE_BUFFER_SIZE?
> + cur_file_pos += len;
> +
> + for (; len > 0; --len)
> + write_buffer[cur_offset++] = *s++;
> +}
>
> - return 0;
> +static void write_32bit_value(uint32_t i) {
> + write_bytes((char*)&i, 4);
> +}
> +
> +static void write_64bit_value(uint64_t i) {
> + write_bytes((char*)&i, 8);
> }
>
> static uint32_t length_of_string(const char *s) {
> @@ -90,25 +122,39 @@ static uint32_t length_of_string(const c
>
> static void write_string(const char *s) {
> uint32_t len = length_of_string(s);
> - write_int32(len);
> - fwrite(s, strlen(s), 1, output_file);
> - fwrite("\0\0\0\0", 4 - (strlen(s) % 4), 1, output_file);
> + write_32bit_value(len);
> + write_bytes(s, strlen(s));
> + write_bytes("\0\0\0\0", 4 - (strlen(s) % 4));
> }
>
> -static uint32_t read_int32() {
> - uint32_t tmp;
> +static uint32_t read_32bit_value() {
> + uint32_t val;
> +
> + if (cur_offset + 4 > WRITE_BUFFER_SIZE)
> + flush_buffer();
>
> - if (fread(&tmp, 1, 4, output_file) != 4)
> + if (new_file)
> return (uint32_t)-1;
>
> - return tmp;
> + val = *(uint32_t*)&write_buffer[cur_offset];
> + cur_file_pos += 4;
> + cur_offset += 4;
> + return val;
> }
>
> -static uint64_t read_into_buffer(uint64_t *buffer, size_t size) {
> - if (fread(buffer, 8, size, output_file) != size)
> - return (uint64_t)-1;
> +static uint64_t read_64bit_value() {
> + uint64_t val;
>
> - return 0;
> + if (cur_offset + 8 > WRITE_BUFFER_SIZE)
> + flush_buffer();
> +
> + if (new_file)
> + return (uint32_t)-1;
> +
> + val = *(uint64_t*)&write_buffer[cur_offset];
> + cur_file_pos += 8;
> + cur_offset += 8;
> + return val;
> }
>
> static char *mangle_filename(const char *orig_filename) {
> @@ -118,13 +164,13 @@ static char *mangle_filename(const char
> int level = 0;
> const char *fname = orig_filename, *ptr = NULL;
> const char *prefix = getenv("GCOV_PREFIX");
> - const char *tmp = getenv("GCOV_PREFIX_STRIP");
> + const char *prefix_strip_str = getenv("GCOV_PREFIX_STRIP");
>
> if (!prefix)
> return strdup(orig_filename);
>
> - if (tmp) {
> - prefix_strip = atoi(tmp);
> + if (prefix_strip_str) {
> + prefix_strip = atoi(prefix_strip_str);
>
> /* Negative GCOV_PREFIX_STRIP values are ignored */
> if (prefix_strip < 0)
> @@ -180,6 +226,7 @@ void llvm_gcda_start_file(const char *or
>
> if (!output_file) {
> /* Try opening the file, creating it if necessary. */
> + new_file = 1;
> output_file = fopen(filename, "w+b");
> if (!output_file) {
> /* Try creating the directories first then opening the file. */
> @@ -194,10 +241,20 @@ void llvm_gcda_start_file(const char *or
> }
> }
>
> + setbuf(output_file, 0);
> +
> + /* Initialize the write buffer. */
> + memset(write_buffer, 0, WRITE_BUFFER_SIZE);
> + fread(write_buffer, 1, WRITE_BUFFER_SIZE, output_file);
> + fseek(output_file, 0L, SEEK_SET);
> + cur_file_pos = 0;
> + cur_offset = 0;
> +
> /* gcda file, version, stamp LLVM. */
> - fwrite("adcg", 4, 1, output_file);
> - fwrite(version, 4, 1, output_file);
> - fwrite("MVLL", 4, 1, output_file);
> + write_bytes("adcg", 4);
> + write_bytes(version, 4);
> + write_bytes("MVLL", 4);
> +
> free(filename);
>
> #ifdef DEBUG_GCDAPROFILING
> @@ -233,6 +290,7 @@ void llvm_gcda_increment_indirect_counte
> void llvm_gcda_emit_function(uint32_t ident, const char *function_name,
> uint8_t use_extra_checksum) {
> uint32_t len = 2;
> +
> if (use_extra_checksum)
> len++;
> #ifdef DEBUG_GCDAPROFILING
> @@ -242,14 +300,14 @@ void llvm_gcda_emit_function(uint32_t id
> if (!output_file) return;
>
> /* function tag */
> - fwrite("\0\0\0\1", 4, 1, output_file);
> + write_bytes("\0\0\0\1", 4);
> if (function_name)
> len += 1 + length_of_string(function_name);
> - write_int32(len);
> - write_int32(ident);
> - write_int32(0);
> + write_32bit_value(len);
> + write_32bit_value(ident);
> + write_32bit_value(0);
> if (use_extra_checksum)
> - write_int32(0);
> + write_32bit_value(0);
> if (function_name)
> write_string(function_name);
> }
> @@ -257,13 +315,13 @@ void llvm_gcda_emit_function(uint32_t id
> void llvm_gcda_emit_arcs(uint32_t num_counters, uint64_t *counters) {
> uint32_t i;
> uint64_t *old_ctrs = NULL;
> + int64_t save_cur_file_pos = cur_file_pos;
> uint32_t val = 0;
> - long pos = 0;
>
> if (!output_file) return;
>
> - pos = ftell(output_file);
> - val = read_int32();
> + flush_buffer();
> + val = read_32bit_value();
>
> if (val != (uint32_t)-1) {
> /* There are counters present in the file. Merge them. */
> @@ -272,33 +330,30 @@ void llvm_gcda_emit_arcs(uint32_t num_co
> return;
> }
>
> - val = read_int32();
> + val = read_32bit_value();
> if (val == (uint32_t)-1 || val / 2 != num_counters) {
> fprintf(stderr, "profiling:invalid number of counters (%d)\n", val);
> return;
> }
>
> old_ctrs = malloc(sizeof(uint64_t) * num_counters);
> + for (i = 0; i < num_counters; ++i)
> + old_ctrs[i] = read_64bit_value();
>
> - if (read_into_buffer(old_ctrs, num_counters) == (uint64_t)-1) {
> - fprintf(stderr, "profiling:invalid number of counters (%d)\n",
> - num_counters);
> - return;
> - }
> - }
> + /* Reset the current buffer and file position. */
> + memset(write_buffer, 0, WRITE_BUFFER_SIZE);
> + cur_file_pos = save_cur_file_pos;
> + cur_offset = 0;
>
> - /* Reset for writing. */
> - fseek(output_file, pos, SEEK_SET);
> + fseek(output_file, cur_file_pos, SEEK_SET);
> + }
>
> /* Counter #1 (arcs) tag */
> - fwrite("\0\0\xa1\1", 4, 1, output_file);
> - write_int32(num_counters * 2);
> - for (i = 0; i < num_counters; ++i)
> + write_bytes("\0\0\xa1\1", 4);
> + write_32bit_value(num_counters * 2);
> + for (i = 0; i < num_counters; ++i) {
> counters[i] += (old_ctrs ? old_ctrs[i] : 0);
> -
> - if (write_from_buffer(counters, num_counters) == (uint64_t)-1) {
> - fprintf(stderr, "profiling:cannot write to output file\n");
> - return;
> + write_64bit_value(counters[i]);
> }
>
> free(old_ctrs);
> @@ -313,7 +368,8 @@ void llvm_gcda_emit_arcs(uint32_t num_co
> void llvm_gcda_end_file() {
> /* Write out EOF record. */
> if (!output_file) return;
> - fwrite("\0\0\0\0\0\0\0\0", 8, 1, output_file);
> + write_bytes("\0\0\0\0\0\0\0\0", 8);
> + flush_buffer();
> fclose(output_file);
> output_file = NULL;
>
>
>
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> llvm-commits at cs.uiuc.edu
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>
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