Any takers on this review? It's a pretty significant change, in terms of both lines of code and improvement.
https://reviews.csiden.org/r/145/ >From the bug report: Currently, every buffer cached in the L2ARC is accompanied by a 240-byte header in memory, leading to very high memory consumption when using very large cache devices. These changes significantly reduce this overhead. Currently: L1-only header = 176 bytes L1 + L2 or L2-only header = 176 bytes + 32 byte checksum + 32 byte l2hdr = 240 bytes Memory-optimized: L1-only header = 176 bytes L1 + L2 header = 176 bytes + 32 byte checksum = 208 bytes L2-only header = 96 bytes + 32 byte checksum = 128 bytes For an average blocksize of 8KB, this means that for the L2ARC, the ratio of metadata to data has gone down from about 2.92% to 1.56%. For a 'storage optimized' EC2 instance with 1600GB of SSD and 60GB of RAM, this means that we expect a completely full L2ARC to use (1600 GB * 0.0156) / 60GB = 41% of the available memory, down from 78%. --matt
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