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define: DUK_USE_LITCACHE_SIZE
introduced: 2.3.0
default: 256
tags:
- performance
- lowmemory
description: >
Size of the literal cache, which maps C literal memory addresses into
pinned duk_hstring heap object addresses. The cache is used when
application code calls one of the duk_xxx_literal() API call variants,
such as duk_push_literal() or duk_get_prop_literal(), to speed up the
string intern check for the literal. In successful cases this caching
makes using duk_xxx_literal() almost as fast as using borrowed heap
pointers with duk_xxx_heapptr().
When this option is defined, duk_hstrings related to literals encountered
in duk_xxx_literal() API calls are automatically pinned between
mark-and-sweep rounds. This accomplishes two things. First, it avoids the
need for cache invalidation for the literal cache in normal operation between
mark-and-sweep rounds. Second, it reduces string table traffic (i.e. freeing
and reallocating) for literals which are likely to occur again and again.
However, the downside is that some strings that may occur only temporarily
will remain pinned until the next mark-and-sweep round. If this matter, you
can avoid it by simply using e.g. duk_xxx_string() when dealing with such
strings.
The literal cache size must be a power of two (2^N).