Similar to the patch last week, this optimizes the pattern verify
operation to use optimized library calls like memcmp(), and only fall
back to byte-by-byte if there is a miscompare to locate it.
This uses the same premise that the pattern is repeated as many times
as possible to do large compares in a single call. For single byte
pattern, the setup fills the pattern space, and verify assumes it is
full.
Tested by running a script which created an 8k file with 4k bs and,
one byte at a time, tried corrupting the pattern and running a read
pass and verified it still found miscompares across the whole range of
the pattern. This was done with a pattern length of 1 and 3 bytes.
In performance tests, this was about 8 times more efficient on
verifies than without this patch.
diff --git a/options.c b/options.c
index 8fb93ca..c3fdb56 100644
--- a/options.c
+++ b/options.c
@@ -698,6 +698,14 @@ static int str_verify_pattern_cb(void *data,
const char *input)
memcpy(&td->o.verify_pattern[i], &td->o.verify_pattern[0], i);
i *= 2;
}
+ if (i == 1) {
+ /*
+ * The code in verify_io_u_pattern assumes a single byte pattern
+ * fills the whole verify pattern buffer.
+ */
+ memset(td->o.verify_pattern, td->o.verify_pattern[0],
+ MAX_PATTERN_SIZE);
+ }
td->o.verify_pattern_bytes = i;
diff --git a/verify.c b/verify.c
index 9ee3bc4..eb8eddc 100644
--- a/verify.c
+++ b/verify.c
@@ -322,14 +322,27 @@ static int verify_io_u_pattern(struct
verify_header *hdr, struct vcont *vc)
struct io_u *io_u = vc->io_u;
char *buf, *pattern;
unsigned int header_size = __hdr_size(td->o.verify);
- unsigned int len, mod, i;
+ unsigned int len, mod, i, size, pattern_size;
pattern = td->o.verify_pattern;
+ pattern_size = td->o.verify_pattern_bytes;
+ if (pattern_size <= 1)
+ pattern_size = MAX_PATTERN_SIZE;
buf = (void *) hdr + header_size;
len = get_hdr_inc(td, io_u) - header_size;
- mod = header_size % td->o.verify_pattern_bytes;
+ mod = header_size % pattern_size;
+
+ for (i = 0; i < len; i += size) {
+ size = pattern_size - mod;
+ if (size > (len - i))
+ size = len - i;
+ if (memcmp(buf + i, pattern + mod, size))
+ // Let the slow compare find the first mismatch byte.
+ break;
+ mod = 0;
+ }
- for (i = 0; i < len; i++) {
+ for (; i < len; i++) {
if (buf[i] != pattern[mod]) {
unsigned int bits;
--
--
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