core.app: remove garbage when using pace_breathing #1287
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The accumulators lastfrees, lastfreebytes, lastfreebits for the counters frees, freebytes and freebits are initialized as Lua numbers but implicitly converted to cdata objects in the assignments in pace_breathing(). This causes allocations that cannot be removed by the sink optimizer. Conversion to Lua numbers avoids this and reduces GC noise.
wingo
reviewed
Mar 2, 2018
| lastfreebits = counter.read(freebits) | ||
| lastfrees = tonumber(counter.read(frees)) | ||
| lastfreebytes = tonumber(counter.read(freebytes)) | ||
| lastfreebits = tonumber(counter.read(freebits)) |
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Is this really what you want? At some point counter.read(frees) will stop being equal to lastfrees because the tonumber() may lose precision. Seems to me better to make lastfrees etc to be uint64_t values in some allocated FFI data.
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I'm not sure this is a problem in practice (it will occur after something like 10 years of processing 14Mpps or something, I guess) but, sure, using a "box" for that would be safe. BTW, why exactly are we keeping lastfreebytes and lastfreebits? They're not used anywhere.
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The accumulators
lastfrees,lastfreebytes,lastfreebitsfor thecounters
frees,freebytesandfreebitsare initialized as Lua numbersbut implicitly converted to cdata objects in the assignments in
pace_breathing(). This causes allocations that cannot be removed bythe sink optimizer. Conversion to Lua numbers avoids this and reduces
GC noise.