Hi,
I was seeing some performance drop during the read verification phase
of a test, and from the code in io_u.c in get_io_u function, we
prepare/populate the buffer in the io_u structure based on the verify
patterns/options.
This makes sense when we are doing writes, but I dont understand why
we do this for the read phase when this data is going to be
overwritten anyways(and in case of truncated reads, we do modify the
buf_len).
So based on that I changed the code to populate the buffer(io_u->buf)
only if its a write with verify enabled.
This works for my tests, but I do not know if there was a reason why
this was populated for reads as well to begin with.
My change:
diff -up io_u.c.orig io_u.c
--- io_u.c.orig 2009-04-27 15:42:11.213724000 -0700
+++ io_u.c 2009-04-27 15:51:34.881647000 -0700
@@ -838,7 +838,7 @@ struct io_u *get_io_u(struct thread_data
f->last_pos = io_u->offset + io_u->buflen;
- if (td->o.verify != VERIFY_NONE)
+ 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);
thanks
-radha
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