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Simplify IO_CACHE by removing current_pos and end_pos as self-references

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These self references were previously used to avoid having to check the
IO_CACHE's type. However, a benchmark shows that on x86 5930k stock,
the type comparison is marginally faster than the double pointer dereference.
For 40 billion my_b_tell calls, the difference is .1 seconds in favor of performing the
type check. (Basically there is no measurable difference)

To prevent bugs from copying the structure using the equals(=) operator,
and having to do the bookkeeping manually, remove these "convenience"
variables.
This commit is contained in:
Vicențiu Ciorbaru
2017-06-18 19:48:57 +03:00
parent b3171607e3
commit 9003869390
6 changed files with 11 additions and 57 deletions
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2
unittest/sql/mf_iocache-t.cc
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@ -93,7 +93,7 @@ IO_CACHE info;
#define CACHE_SIZE 16384
#define INFO_TAIL ", pos_in_file = %llu, pos_in_mem = %lu", \
info.pos_in_file, (ulong) (*info.current_pos - info.request_pos)
info.pos_in_file, (ulong) ((info.type == READ_CACHE ? info.read_pos : info.write_pos) - info.request_pos)
#define FILL 0x5A