On 12/20/19 10:44 PM, Josef Bacik wrote:
On 12/20/19 12:06 AM, Anand Jain wrote:
As of now we use %pid method to read stripped mirrored data. So
application's process id determines the stripe id to be read. This type
of routing typically helps in a system with many small independent
applications tying to read random data. On the other hand the %pid
based read IO distribution policy is inefficient if there is a single
application trying to read large data and the overall disk bandwidth
remains under utilized.
So this patch introduces a framework where we could add more readmirror
policies, such as routing the IO based on device's waitqueue or manual
when we have a read-preferred device or a policy based on the target
storage caching.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/volumes.c | 16 +++++++++++++++-
fs/btrfs/volumes.h | 8 ++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c95e47aa84f8..0c6caae29248 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1162,6 +1162,8 @@ static int open_fs_devices(struct
btrfs_fs_devices *fs_devices,
fs_devices->opened = 1;
fs_devices->latest_bdev = latest_dev->bdev;
fs_devices->total_rw_bytes = 0;
+ /* Set the default readmirror policy */
+ atomic_set(&fs_devices->readmirror, BTRFS_READMIRROR_DEFAULT);
There's no reason for this to be atomic, it's just a behavior change, if
you really want to be super safe use READ_ONCE/WRITE_ONCE and have
readmirror be your enum. Thanks,
Agreed fs_devices::readmirror doesn't have to be atmoic_t. Fixed this
to declare it as u8 in v2.
Thanks, Anand
Josef
