The following changes since commit 23f394d5d70902c6f1d71ac03fa1d70e13c9c0b9:
Scramble on a 512b boundary (2011-09-16 22:47:15 +0200)
are available in the git repository at:
git://git.kernel.dk/fio.git master
Jens Axboe (2):
Add option for controlling buffer scrambling
Scramble fix
HOWTO | 7 +++++++
fio.1 | 7 +++++++
fio.h | 1 +
io_u.c | 23 ++++++++++++++---------
options.c | 7 +++++++
5 files changed, 36 insertions(+), 9 deletions(-)
---
Diff of recent changes:
diff --git a/HOWTO b/HOWTO
index b67a201..cc2df9b 100644
--- a/HOWTO
+++ b/HOWTO
@@ -481,6 +481,13 @@ refill_buffers If this option is given, fio will refill the IO buffers
isn't specified, naturally. If data verification is enabled,
refill_buffers is also automatically enabled.
+scramble_buffers=bool If refill_buffers is too costly and the target is
+ using data deduplication, then setting this option will
+ slightly modify the IO buffer contents to defeat normal
+ de-dupe attempts. This is not enough to defeat more clever
+ block compression attempts, but it will stop naive dedupe of
+ blocks. Default: true.
+
nrfiles=int Number of files to use for this job. Defaults to 1.
openfiles=int Number of files to keep open at the same time. Defaults to
diff --git a/fio.1 b/fio.1
index e8fb57f..dc10b40 100644
--- a/fio.1
+++ b/fio.1
@@ -329,6 +329,13 @@ default is to only fill it at init time and reuse that data. Only makes sense
if zero_buffers isn't specified, naturally. If data verification is enabled,
refill_buffers is also automatically enabled.
.TP
+.BI scramble_buffers \fR=\fPbool
+If \fBrefill_buffers\fR is too costly and the target is using data
+deduplication, then setting this option will slightly modify the IO buffer
+contents to defeat normal de-dupe attempts. This is not enough to defeat
+more clever block compression attempts, but it will stop naive dedupe
+of blocks. Default: true.
+.TP
.BI nrfiles \fR=\fPint
Number of files to use for this job. Default: 1.
.TP
diff --git a/fio.h b/fio.h
index e93e8f3..022ba57 100644
--- a/fio.h
+++ b/fio.h
@@ -348,6 +348,7 @@ struct thread_options {
enum fio_fallocate_mode fallocate_mode;
unsigned int zero_buffers;
unsigned int refill_buffers;
+ unsigned int scramble_buffers;
unsigned int time_based;
unsigned int disable_lat;
unsigned int disable_clat;
diff --git a/io_u.c b/io_u.c
index f4c4aa2..38efcc1 100644
--- a/io_u.c
+++ b/io_u.c
@@ -1129,6 +1129,7 @@ static int check_get_verify(struct thread_data *td, struct io_u *io_u)
static void small_content_scramble(struct io_u *io_u)
{
unsigned int i, nr_blocks = io_u->buflen / 512;
+ unsigned long long boffset;
unsigned int offset;
void *p, *end;
@@ -1136,20 +1137,23 @@ static void small_content_scramble(struct io_u *io_u)
return;
p = io_u->xfer_buf;
+ boffset= io_u->offset;
+
for (i = 0; i < nr_blocks; i++) {
/*
* Fill the byte offset into a "random" start offset of
* the buffer, given by the product of the usec time
* and the actual offset.
*/
- offset = (io_u->start_time.tv_usec * io_u->offset) & 511;
+ offset = (io_u->start_time.tv_usec ^ boffset) & 511;
if (offset >= 512 - sizeof(unsigned long long))
offset -= sizeof(unsigned long long);
- *((unsigned long long *) p + offset) = io_u->offset;
+ *((unsigned long long *) p + offset) = boffset;
end = p + 512 - sizeof(io_u->start_time);
memcpy(end, &io_u->start_time, sizeof(io_u->start_time));
p += 512;
+ boffset += 512;
}
}
@@ -1203,13 +1207,14 @@ struct io_u *get_io_u(struct thread_data *td)
f->last_start = io_u->offset;
f->last_pos = io_u->offset + io_u->buflen;
- if (td->o.verify != VERIFY_NONE && io_u->ddir == DDIR_WRITE)
- populate_verify_io_u(td, io_u);
- else if (td->o.refill_buffers && io_u->ddir == DDIR_WRITE)
- io_u_fill_buffer(td, io_u, io_u->xfer_buflen);
- else if (io_u->ddir == DDIR_WRITE)
- do_scramble = 1;
- else if (io_u->ddir == DDIR_READ) {
+ if (io_u->ddir == DDIR_WRITE) {
+ if (td->o.verify != VERIFY_NONE)
+ populate_verify_io_u(td, io_u);
+ else if (td->o.refill_buffers)
+ io_u_fill_buffer(td, io_u, io_u->xfer_buflen);
+ else if (td->o.scramble_buffers)
+ do_scramble = 1;
+ } else if (io_u->ddir == DDIR_READ) {
/*
* Reset the buf_filled parameters so next time if the
* buffer is used for writes it is refilled.
diff --git a/options.c b/options.c
index 74c24d0..5252477 100644
--- a/options.c
+++ b/options.c
@@ -1967,6 +1967,13 @@ static struct fio_option options[FIO_MAX_OPTS] = {
.help = "Refill IO buffers on every IO submit",
},
{
+ .name = "scramble_buffers",
+ .type = FIO_OPT_BOOL,
+ .off1 = td_var_offset(scramble_buffers),
+ .help = "Slightly scramble buffers on every IO submit",
+ .def = "1",
+ },
+ {
.name = "clat_percentiles",
.type = FIO_OPT_BOOL,
.off1 = td_var_offset(clat_percentiles),
--
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