Fixes some typos as found by codespell run on the code.
In this commit, I was hoping to fix only comments, not user-visible alerts, output, etc.
Follow-up commits will take care of them.
Refs: https://github.com/scylladb/scylladb/issues/16255
Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>
in C++20, compiler generate operator!=() if the corresponding
operator==() is already defined, the language now understands
that the comparison is symmetric in the new standard.
fortunately, our operator!=() is always equivalent to
`! operator==()`, this matches the behavior of the default
generated operator!=(). so, in this change, all `operator!=`
are removed.
in addition to the defaulted operator!=, C++20 also brings to us
the defaulted operator==() -- it is able to generated the
operator==() if the member-wise lexicographical comparison.
under some circumstances, this is exactly what we need. so,
in this change, if the operator==() is also implemented as
a lexicographical comparison of all memeber variables of the
class/struct in question, it is implemented using the default
generated one by removing its body and mark the function as
`default`. moreover, if the class happen to have other comparison
operators which are implemented using lexicographical comparison,
the default generated `operator<=>` is used in place of
the defaulted `operator==`.
sometimes, we fail to mark the operator== with the `const`
specifier, in this change, to fulfil the need of C++ standard,
and to be more correct, the `const` specifier is added.
also, to generate the defaulted operator==, the operand should
be `const class_name&`, but it is not always the case, in the
class of `version`, we use `version` as the parameter type, to
fulfill the need of the C++ standard, the parameter type is
changed to `const version&` instead. this does not change
the semantic of the comparison operator. and is a more idiomatic
way to pass non-trivial struct as function parameters.
please note, because in C++20, both operator= and operator<=> are
symmetric, some of the operators in `multiprecision` are removed.
they are the symmetric form of the another variant. if they were
not removed, compiler would, for instance, find ambiguous
overloaded operator '=='.
this change is a cleanup to modernize the code base with C++20
features.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes#13687
these warnings are found by Clang-17 after removing
`-Wno-unused-lambda-capture` and '-Wno-unused-variable' from
the list of disabled warnings in `configure.py`.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
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
Whenever a node_head_ptr is assigned to nil_root, the _backref inside it is
overwritten. But since nil_root is shared between shards, this causes severe
cache line bouncing. (It was observed to reduce the total write throughput
of Scylla by 90% on a large NUMA machine).
This backreference is never read anyway, so fix this bug by not writing it.
Fixes#9252Closes#9246
The radix tree template defines a nested class template array_of;
both a generic template and a fully specialized version. However,
gcc (I believe correctly) rejects the fully specialized template
that happens to be a member of another class template.
As it happens, we don't really need a template here at all. Define
a non-template class for each of the cases we need, and use
std::conditional_t to select the type we need.
The `direct_layout` and `indirect_layout` template classes accept
a template parameter named `Layout` of type `layout`, and re-export
`Layout` as a static data member named `layout`. This redefinition
of `layout` is disliked by gcc. Fix by renaming the static data member
to `this_layout` and adjust all references.
Usually lsa allocation is performed with the construct() helper that
allocates a sizeof(T) slot and constructs it in place. Some rare
objects have dynamic size, so they are created by alloc()ating a
slot of some specific size and (!) must provide the correct overload
of size_for_allocation_strategy that reports back the relevant
storage size.
This "must provide" is not enforced, if missed a default sizer would
be instantiated, but won't work properly. This patch makes all users
of alloc() conform to DynamicObject concept which requires the
presense of .storage_size() method to tell that size.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Todays alloc() accepts migrate-fn, size and alignment. All the callers
don't really need to provide anything special for the migrate-fn and
are just happy with default alignof() for alignment. The simplification
is in providing alloc() that only accepts size arg and does the rest
itself.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
After switching cells storage onto compact radix tree it
becomes useful to know the tree nodes' sizes.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The tree uses integral type as a search key. On each level the local index
is next 7 bits from the key, respectively for 32-bit key we have 5 levels.
The tree uses 2 memory packing techniques -- prefix compaction and growing
node layouts.
The prefix compaction is used when a node has only one child. In this case
such a node is replaced in its parent with this only child and the child in
question keeps "prefix:length" pair on board, that's used to check if the
short-cut lookup took the correct path.
The growing node layouts makes the nodes occupy as much memory as needed
to keep the _present_ keys and there are 2 kinds of layouts.
Direct layout is array, intra-node search is plain indexing. The layout
storage grows in vector-like manner, but there's a special case for the
maximum-sized layout that helps avoiding some boundary checks.
Indirect layout keeps two arrays on board -- with values and with indices.
The intra-node search is thus a lookup in the latter array first. This
layout is used to save memory for sparse keys. Lookup is optimized with
SIMD instructions.
Inner nodes use direct layouts, as they occupy ~1% of memory and thus
need not to be memory efficient. At the same time lookup of a key in the
tree potentially walks several inner nodes, so speeding up search for
them is beneficial.
Leaf nodes are indirect, since they are 99% of memory and thus need to
be packed well. The single indirect lookup when searching in the tree
doesn't slow things down notably even on insertion stress test.
Said that
* inner nodes are: header + 4 / 8 / 16 / 32 / 64 / 128 pointers
* leaf nodes are : header + 4 / 8 / 16 / 32 bytes + <same nr> objects
or header + 16 bytes bitmap + 128 objects
The header is
- backreference (8 bytes)
- prefix (4 bytes)
- size, layout, capacity (1 byte each)
The iterator is one-direction (for simplicity) but it enough for its main
target -- the sparse array of cells on a row. Also the iterator has an
.index() method that reports back the index of the entry at which it points.
This greatly simplifies the tree scans by the class row further.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
