[LU-9161] mount_utils_ldiskfs.c is_feature_enabled() should pass '-c' to debugfs Created: 27/Feb/17 Updated: 14/Mar/17 Resolved: 14/Mar/17 |
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| Status: | Resolved |
| Project: | Lustre |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | Lustre 2.10.0 |
| Type: | Bug | Priority: | Minor |
| Reporter: | John Hammond | Assignee: | WC Triage |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | easy | ||
| Issue Links: |
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| Severity: | 3 | ||||||||
| Rank (Obsolete): | 9223372036854775807 | ||||||||
| Description |
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The meta_bg feature unfortunately fragments the group descriptor block across the whole filesystem, rather than continuously at the start of the device. This causes a large amount of seeking (at least 32768 seeks for a 256TB filesystem). Skipping the loading of inode tables and bitmaps via -c will avoid reading many GB of data. |
| Comments |
| Comment by Andreas Dilger [ 28/Feb/17 ] |
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Instead of running debugfs in a shell and parsing the text output, we might consider just reading struct ext4_super_block at offset 1024 bytes, and then checking the binary feature flags directly. That will avoid all overhead from reading the group descriptors and any other metadata. Another alternative is to modify debugfs to avoid loading the bitmaps until required (possibly only starting a background prefetch at filesystem open time) as an extension of the |
| Comment by Gerrit Updater [ 28/Feb/17 ] |
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Andreas Dilger (andreas.dilger@intel.com) uploaded a new patch: https://review.whamcloud.com/25671 |
| Comment by Gerrit Updater [ 14/Mar/17 ] |
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Oleg Drokin (oleg.drokin@intel.com) merged in patch https://review.whamcloud.com/25671/ |
| Comment by Peter Jones [ 14/Mar/17 ] |
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Landed for 2.10 |