Commit Graph

6 Commits

Author SHA1 Message Date
Eric Blake
f3e4ce4af3 blockjob: Track job ratelimits via bytes, not sectors
The user interface specifies job rate limits in bytes/second.
It's pointless to have our internal representation track things
in sectors/second, particularly since we want to move away from
sector-based interfaces.

Fix up a doc typo found while verifying that the ratelimit
code handles the scaling difference.

Repetition of expressions like 'n * BDRV_SECTOR_SIZE' will be
cleaned up later when functions are converted to iterate over
images by bytes rather than by sectors.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-07-10 13:18:06 +02:00
Sascha Silbe
f14a39ccb9 Improve block job rate limiting for small bandwidth values
ratelimit_calculate_delay() previously reset the accounting every time
slice, no matter how much data had been processed before. This had (at
least) two consequences:

1. The minimum speed is rather large, e.g. 5 MiB/s for commit and stream.

   Not sure if there are real-world use cases where this would be a
   problem. Mirroring and backup over a slow link (e.g. DSL) would
   come to mind, though.

2. Tests for block job operations (e.g. cancel) were rather racy

   All block jobs currently use a time slice of 100ms. That's a
   reasonable value to get smooth output during regular
   operation. However this also meant that the state of block jobs
   changed every 100ms, no matter how low the configured limit was. On
   busy hosts, qemu often transferred additional chunks until the test
   case had a chance to cancel the job.

Fix the block job rate limit code to delay for more than one time
slice to address the above issues. To make it easier to handle
oversized chunks we switch the semantics from returning a delay
_before_ the current request to a delay _after_ the current
request. If necessary, this delay consists of multiple time slice
units.

Since the mirror job sends multiple chunks in one go even if the rate
limit was exceeded in between, we need to keep track of the start of
the current time slice so we can correctly re-compute the delay for
the updated amount of data.

The minimum bandwidth now is 1 data unit per time slice. The block
jobs are currently passing the amount of data transferred in sectors
and using 100ms time slices, so this translates to 5120
bytes/second. With chunk sizes usually being O(512KiB), tests have
plenty of time (O(100s)) to operate on block jobs. The chance of a
race condition now is fairly remote, except possibly on insanely
loaded systems.

Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Message-id: 1467127721-9564-2-git-send-email-silbe@linux.vnet.ibm.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2016-07-13 13:41:38 +02:00
Markus Armbruster
175de52487 Clean up decorations and whitespace around header guards
Cleaned up with scripts/clean-header-guards.pl.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
2016-07-12 16:20:46 +02:00
Alex Bligh
bc72ad6754 aio / timers: Switch entire codebase to the new timer API
This is an autogenerated patch using scripts/switch-timer-api.

Switch the entire code base to using the new timer API.

Note this patch may introduce some line length issues.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:14:24 +02:00
Dietmar Maurer
e3980e28bb stream: fix ratelimit_set_speed
The formula to compute slice_quota was wrong since commit 6ef228fc.

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-11-30 11:33:24 +01:00
Paolo Bonzini
6ef228fc0d stream: move rate limiting to a separate header file
Make the code reusable.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-06-15 14:03:42 +02:00