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  1. 24 Apr, 2015 3 commits
    • Eric Sandeen's avatar
      fix I_DIO_WAKEUP definition · ac74d8d6
      Eric Sandeen authored 
      I_DIO_WAKEUP is never directly used, but fix it up anyway.
Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      ac74d8d6
    • Jens Axboe's avatar
      direct-io: only inc/dec inode->i_dio_count for file systems · fe0f07d0
      Jens Axboe authored 
      do_blockdev_direct_IO() increments and decrements the inode
->i_dio_count for each IO operation. It does this to protect against
truncate of a file. Block devices don't need this sort of protection.

For a capable multiqueue setup, this atomic int is the only shared
state between applications accessing the device for O_DIRECT, and it
presents a scaling wall for that. In my testing, as much as 30% of
system time is spent incrementing and decrementing this value. A mixed
read/write workload improved from ~2.5M IOPS to ~9.6M IOPS, with
better latencies too. Before:

clat percentiles (usec):
 |  1.00th=[   33],  5.00th=[   34], 10.00th=[   34], 20.00th=[   34],
 | 30.00th=[   34], 40.00th=[   34], 50.00th=[   35], 60.00th=[   35],
 | 70.00th=[   35], 80.00th=[   35], 90.00th=[   37], 95.00th=[   80],
 | 99.00th=[   98], 99.50th=[  151], 99.90th=[  155], 99.95th=[  155],
 | 99.99th=[  165]

After:

clat percentiles (usec):
 |  1.00th=[   95],  5.00th=[  108], 10.00th=[  129], 20.00th=[  149],
 | 30.00th=[  155], 40.00th=[  161], 50.00th=[  167], 60.00th=[  171],
 | 70.00th=[  177], 80.00th=[  185], 90.00th=[  201], 95.00th=[  270],
 | 99.00th=[  390], 99.50th=[  398], 99.90th=[  418], 99.95th=[  422],
 | 99.99th=[  438]

In other setups, Robert Elliott reported seeing good performance
improvements:

https://lkml.org/lkml/2015/4/3/557

The more applications accessing the device, the worse it gets.

Add a new direct-io flags, DIO_SKIP_DIO_COUNT, which tells
do_blockdev_direct_IO() that it need not worry about incrementing
or decrementing the inode i_dio_count for this caller.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Elliott, Robert (Server Storage) <elliott@hp.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      fe0f07d0
    • Johannes Berg's avatar
      fs/9p: fix readdir() · 8e3c5005
      Johannes Berg authored 
      Al Viro's IOV changes broke 9p readdir() because the new code
didn't abort the read when it returned nothing. The original
code checked if the combined error/length was <= 0 but in the
new code that accidentally got changed to just an error check.

Add back the return from the function when nothing is read.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Fixes: e1200fe6 ("9p: switch p9_client_read() to passing struct iov_iter *")
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      8e3c5005
  3. 15 Apr, 2015 24 commits
  5. 12 Apr, 2015 13 commits
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