edaec84225
Before my ZIL space optimization few years ago 128KB writes were logged as two 64KB+ records in two 128KB log blocks. After that change it became ~127KB+/1KB+ in two 128KB log blocks to free space in the second block for another record. Unfortunately in case of 128KB only writes, when space in the second block remained unused, that change increased write latency by unbalancing checksum computation and write times between parallel threads. It also didn't help with SLOG space efficiency in that case. This change introduces new 68KB log block size, used for both writes below 67KB and 128KB-sharp writes. Writes of 68-127KB are still using one 128KB block to not increase processing overhead. Writes above 131KB are still using full 128KB blocks, since possible saving there is small. Mixed loads will likely also fall back to previous 128KB, since code uses maximum of the last 16 requested block sizes. Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Closes #9409 |
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