Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Streaming is handled by just once group for CPU scheduling, so
separating it into read and write classes for I/O is artificial, and
inflates the resources we allow for streaming if both reads and writes
happen at the same time.
Merge both classes into one class ("streaming") and adjust callers. The
merged class has 200 shares, so it reduces streaming bandwidth if both
directions are active at the same time (which is rare; I think it only
happens in view building).
Make the constructor out-of-line and clean up includes made redundant.
This removes an include of Seastar's heavy reactor.hh from a header.
Ref #1
Message-Id: <20200329173711.16949-1-avi@scylladb.com>
Technically all that matters is the proportion among the shares so this
change is functionally a noop. However, The CPU scheduler being proposed
has shares that go all the way up to 1000. In the hopes of being able to
unify I/O and CPU controllers one day, this patch brings the I/O shares
more in line with what Avi is doing for the CPU scheduler.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
- introcduced "seastarx.hh" header, which does a "using namespace seastar";
- 'net' namespace conflicts with seastar::net, renamed to 'netw'.
- 'transport' namespace conflicts with seastar::transport, renamed to
cql_transport.
- "logger" global variables now conflict with logger global type, renamed
to xlogger.
- other minor changes
Streaming has currently one class, that can be used to contain the read
operations being generated by the streaming process. Those reads come from two
places:
- checksums (if doing repair)
- reading mutations to be sent over the wire.
Depending on the amount of data we're dealing with, that can generate a
significant chunk of data, with seconds worth of backlog, and if we need to
have the incoming writes intertwined with those reads, those can take a long
time.
Even if one node is only acting as a receiver, it may still read a lot for the
checksums - if we're talking about repairs, those are coming from the
checksums.
However, in more complicated failure scenarios, it is not hard to imagine a
node that will be both sending and receiving a lot of data.
The best way to guarantee progress on both fronts, is to put both kinds of
operations into different classes.
This patch introduces a new write class, and rename the old read class so it
can have a more meaningful name.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
After the introduction of the Fair I/O Queueing mechanism in Seastar,
it is possible to add requests to a specific priority class, that will
end up being serviced fairly.
This patch introduces a Priority Manager service, that manages the priority
each class of request will get. At this moment, having a class for that may
sound like an overkill. However, the most interesting feature of the Fair I/O
queue comes from being able to adjust the priorities dynamically as workloads
changes: so we will benefit from having them all in the same place.
This is designed to behave like one of our services, with the exception that
it won't use the distributed interface. This is mainly because there is no
reason to introduce that complexity at this point - since we can do thread local
registration as we have been doing in Seastar, and because that would require us
to change most of our tests to start a new service.
Signed-off-by: Glauber Costa <glauber@scylladb.com>
