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Differential D20121

Optimize padding in powerpc busdma_machdep.c
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Authored by bdragon on May 1 2019, 4:14 AM.
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rS347079: powerpc: Optimize padding in bus_dma_tag
Summary

Noticed this while manually inspecting DMA tags.

Save 64 bytes of padding (32b after nsegments due to alignment requirements of next member, 32b after map_count due to alignment requirements of next member due to odd number of contig. ints.)

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bdragon created this revision.May 1 2019, 4:14 AM
Herald added a subscriber: imp. · View Herald TranscriptMay 1 2019, 4:14 AM
jhibbits accepted this revision.May 1 2019, 2:10 PM

From my count it saves 8 bytes, not 64. I don't think it's a significant issue, given the size of the structure already, but it's not a bad change, and does allow for better packing.

This revision is now accepted and ready to land.May 1 2019, 2:10 PM
bdragon added a comment.May 1 2019, 6:02 PM

Yeah I meant bits, not bytes. 64 bits. 8 bytes.

Closed by commit rS347079: powerpc: Optimize padding in bus_dma_tag (authored by jhibbits). · Explain WhyMay 4 2019, 2:45 AM
This revision was automatically updated to reflect the committed changes.

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head/
sys/
powerpc/
powerpc/
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head/sys/powerpc/powerpc/busdma_machdep.c

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