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Slightly improve dnode hash #16131

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May 1, 2024
Merged

Slightly improve dnode hash #16131

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6 changes: 3 additions & 3 deletions module/zfs/dmu_objset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -400,10 +400,10 @@ dnode_hash(const objset_t *os, uint64_t obj)

ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
/*
* The low 6 bits of the pointer don't have much entropy, because
* the objset_t is larger than 2^6 bytes long.
* The lower 11 bits of the pointer don't have much entropy, because
* the objset_t is more than 1KB long and so likely aligned to 2KB.
*/
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (osv >> 6)) & 0xFF];
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (osv >> 11)) & 0xFF];
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (obj >> 0)) & 0xFF];
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (obj >> 8)) & 0xFF];
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (obj >> 16)) & 0xFF];
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