Commit 1671d9c433 (not on any release branch)
accidentally bumped the idle memtable flush cpu shares to 100 (representing
10%), causing flushes to be too when they don't comsume too much cpu.
Fixes#3243.
Message-Id: <20180408104601.9607-1-avi@scylladb.com>
We have had so far an I/O controller, for compactions and memtables, and
a CPU controller, for memtables only -- since the scheduling was still
quota-based.
Now that the CPU scheduler is fully functional, it is time to do away
with the differences and integrate them both into one. We now have a
memtable controller and a compaction controller, and they control both
CPU and I/O.
In the future, we may want to control processes that don't do one of
them, like cache updates. If that ever happens, we'll try to make
controlling one of them optional. But for now, since the I/O and CPU
controllers for our main two processes would look exactly the same we
should integrate them.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
We have merged the I/O controller without this, but we want to integrate
the CPU and I/O controllers into one. Currently, the quota can be
statically set for the CPU controller. For now, until we gain more
experience with it we should allow a static value to override the
controller's output as well.
That is particularly important since we don't yet control some
strategies like LCS and the time-based ones. Users in the field may be
using one of those strategies with a static value for background quota.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Right now CPU and I/O controllers have slightly different control points
for no good reason. Let's use the CPU controller ones as the standard, as
we have been using it in the field for longer and trust it more.
The end goal is to fully integrate them.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
It no longer makes sense now that we have the full scheduler +
controllers. In its lieu, we will provide an option to statically set
the controller's shares as a safe guard against us getting this wrong.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Set up scheduling groups for streaming, compaction, memtable flush, query,
and commitlog.
The background writer scheduling group is retired; it is split into
the memtable flush and compaction groups.
Comments from Glauber:
This patch is based in a patch from Avi with the same subject, but the
differences are signficant enough so that I reset authorship. In
particular:
1) A bug/regression is fixed with the boundary calculations for the
memtable controller sampling function.
2) A leftover is removed, where after flushing a memtable we would
go back to the main group before going to the cache group again
3) As per Tomek's suggestion, now the submission of compactions
themselves are run in the compaction scheduling group. Having that
working is what changes this patch the most: we now store the
scheduling group in the compaction manager and let the compaction
manager itself enforce the scheduling group.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
thread_scheduling_groups are converted to plain scheduling_group. Due to
differences in initialization (scheduling_group initializtion defers), we
create the scheduling_groups in main.cc and propagate them to users via
a new class database_config.
The sstable writer loses its thread_scheduling_group parameter and instead
inherits scheduling from its caller.
Since shares are in the 1-1000 range vs. 0-1 for thread scheduling quotas,
the flush controller was adjusted to return values within the higher ranges.
The algorithm and principle of operation is the same as the CPU
controller. It is, however, always enabled and we will operate on
I/O shares.
I/O-bound workloads are expected to hit the maximum once virtual
dirty fills up and stay there while the load is steady.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
Compactions can be a heavy disk user and the I/O scheduler can always
guarantee that it uses its fair share of disk.
Such fair share can, however, be a lot more than what compaction indeed
need. This patch draws on the controllers infrastructure to adjust the
I/O shares that the compaction class will get so that compaction
bandwidth is dynamically adjusted.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
The control algorithm we are using for memtables have proven itself
quite successful. We will very likely use the same for other processes,
like compactions.
Make the code a bit more generic, so that a new controller has to only
set the desired parameters
Signed-off-by: Glauber Costa <glauber@scylladb.com>
