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[Qemu-devel] [PATCH RESEND for 2.3 3/6] xbzrle: don't check the value in
From: |
arei.gonglei |
Subject: |
[Qemu-devel] [PATCH RESEND for 2.3 3/6] xbzrle: don't check the value in the vm ram repeatedly |
Date: |
Mon, 24 Nov 2014 19:55:49 +0800 |
From: ChenLiang <address@hidden>
xbzrle_encode_buffer checks the value in the vm ram repeatedly.
It is risk if runs xbzrle_encode_buffer on changing data.
Signed-off-by: ChenLiang <address@hidden>
Signed-off-by: Gonglei <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
---
xbzrle.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/xbzrle.c b/xbzrle.c
index 8e220bf..d27a140 100644
--- a/xbzrle.c
+++ b/xbzrle.c
@@ -27,7 +27,7 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf,
int slen,
uint8_t *dst, int dlen)
{
uint32_t zrun_len = 0, nzrun_len = 0;
- int d = 0, i = 0;
+ int d = 0, i = 0, j;
long res;
uint8_t *nzrun_start = NULL;
@@ -82,6 +82,8 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf,
int slen,
if (d + 2 > dlen) {
return -1;
}
+ i++;
+ nzrun_len++;
/* not aligned to sizeof(long) */
res = (slen - i) % sizeof(long);
while (res && old_buf[i] != new_buf[i]) {
@@ -96,14 +98,18 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t
*new_buf, int slen,
unsigned long mask = (unsigned long)0x0101010101010101ULL;
while (i < slen) {
unsigned long xor;
+ uint8_t *xor_ptr = (uint8_t *)(&xor);
xor = *(unsigned long *)(old_buf + i)
^ *(unsigned long *)(new_buf + i);
if ((xor - mask) & ~xor & (mask << 7)) {
/* found the end of an nzrun within the current long */
- while (old_buf[i] != new_buf[i]) {
- nzrun_len++;
- i++;
+ for (j = 0; j < sizeof(long); j++) {
+ if (0 == xor_ptr[j]) {
+ break;
+ }
}
+ i += j;
+ nzrun_len += j;
break;
} else {
i += sizeof(long);
@@ -120,6 +126,8 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t
*new_buf, int slen,
memcpy(dst + d, nzrun_start, nzrun_len);
d += nzrun_len;
nzrun_len = 0;
+ i++;
+ zrun_len++;
}
return d;
--
1.7.12.4
- [Qemu-devel] [PATCH RESEND for 2.3 0/6] xbzrle: optimize the xbzrle, arei.gonglei, 2014/11/24
- [Qemu-devel] [PATCH RESEND for 2.3 6/6] migration: clear the dead code, arei.gonglei, 2014/11/24
- [Qemu-devel] [PATCH RESEND for 2.3 5/6] migration: optimize xbzrle by reducing data copy, arei.gonglei, 2014/11/24
- [Qemu-devel] [PATCH RESEND for 2.3 1/6] xbzrle: optimize XBZRLE to decrease the cache misses, arei.gonglei, 2014/11/24
- [Qemu-devel] [PATCH RESEND for 2.3 3/6] xbzrle: don't check the value in the vm ram repeatedly,
arei.gonglei <=
- [Qemu-devel] [PATCH RESEND for 2.3 2/6] xbzrle: rebuild the cache_is_cached function, arei.gonglei, 2014/11/24
- [Qemu-devel] [PATCH RESEND for 2.3 4/6] xbzrle: check 8 bytes at a time after an concurrency scene, arei.gonglei, 2014/11/24