Change ZVOL to use _by_dnode() methods #240
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This continues what was started in 0eef1bde31d67091d3deed23fe2394f5a8bf2276 by fully converting zvols to avoid unnecessary dnode_hold() calls. This saves a small amount of CPU time and slightly improves latencies of operations on zvols. Reviewed-by: Brian Behlendorf <[email protected]> Signed-off-by: Richard Yao <[email protected]> Closes #6058 Porting-notes: Cleaned up previous style, which was based on OSX. Since we can use the standard uio call, we should take advantage of that. Additionally deleted all the symlink code, as that is specific to OSX. Ported-by: Jorgen Lundman <[email protected]>
We can improve the performance of writes to zvols by using dmu_tx_hold_write_by_dnode() instead of dmu_tx_hold_write(). This reduces lock contention on the first block of the dnode object, and also reduces the amount of CPU needed. The benefit will be highest with multi-threaded async writes (i.e. writes that don't call zil_commit()). Signed-off-by: Matthew Ahrens <[email protected]>
$ ./zfs create -s -V 3GB -b 2048 tank/vol Warning: volblocksize (2048) < ashift (12 / 4096) means all writes are amplified and space wasted.
lundman
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Apr 11, 2020
| "volblocksize (%llu) < ashift (%llu / %llu)\n" | ||
| "means all writes are amplified and space wasted.\n"), | ||
| blocksize, ashift, 1ULL << ashift); | ||
| } |
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@ahrens You might want to de-ESOL the text... :)
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Waiting for approval in openzfs/zfs#10199 |
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Which reduces the contention behind the ZVOL_OBJ mutex.