When upgrading a cluster to 7.0 which has stale data from 6.2, we don't
want to calculate an xxHash64 checksum for every page that's read. By
clearing the first 8 bits of all checksums written using xxHash64, the
server can skip this checksum in 255/256 cases when reading pages
written from version <=6.2.
This reverts commit e258dffc65a2cf3e7768f2c9f833f9f553a52d74, reversing
changes made to 0e96233015c25608df620a8c1b81f9945bbd6a33.
SS commit seems to be causing write performance degredation.
Using the recently added IndexedSet::const_iterator
(https://github.com/apple/foundationdb/pull/3185), we can improve the
const-correctness of many functions. In this PR const is added where
applicable. Also, wherever I came across the following while adding
const, I made the following changes:
- virtual function overrides are marked as override
- NULL is replaced with nullptr
- git clang-format is applied
So that we can use it from a piece of flow code without breaking module
boundaries.
Also rename generated-constants to crc32c-generated-constants so that
it's more apparent that they're related files.
Future versions of FDB will write sqlite pages with CRC32 checksums. In
order to roll back to this version from a version that writes CRC32
checksums, this version must be able to verify those checksums.
This is the first part of making `TraceEvent` cheaper. The main idea is
to defer calls to any code that formats string. These are the main
changes:
- TraceEvent::detail now takes a c-string instead of std::string for
literals. This prevents unnecessary allocations if the trace is not
going to be printed in the first place (for example for SevDebug).
Before that `detail` expected a `std::string` as key, which mean that
any string literal would be copied on each call.
- Templates Traceable and SpecialTraceMetricType. These templates can be
specialized for any type that needs to be printed. The actual
formatting will be deferred to after the `enabled` check. This
provides two benefits: (1) if a TraceEvent is disabled, we don't pay
for the formatting and (2) TraceEvent can trace types that it doesn't
know about.
- TraceEvent::enabled will be set in the constructor if the Severity is
passed. This will make sure that `TraceEvent::init` is not called.
- `TraceEvent::detail` will be inlined. So for disabled TraceEvent
calls, a call to detail will only introduce a if-branch which is much
cheaper than a function call.
Remove the use of relative paths. A header at foo/bar.h could be included by
files under foo/ with "bar.h", but would be included everywhere else as
"foo/bar.h". Adjust so that every include references such a header with the
latter form.
Signed-off-by: Robert Escriva <rescriva@dropbox.com>
