Move key's headers check outside of eblob_fill_write_control_from_ram #165
Description
This check was added in 9685074 and it is intended to determine broken records and incongruity between index and blob.
This check should be moved outside of eblob_fill_write_control_from_ram because eblob_fill_write_control_from_ram is always called under global lock on b->lock and additional seek under this lock leads to degradation of response time.
Our load tests showed follow degradation:
| quantile | original v0.23.10 | v0.23.10 with reverted 9685074 |
|---|---|---|
| 99% | 82.0 ms | 26.0 ms (-56.0) |
| 98% | 27.0 ms | 16.0 ms (-11.0) |
| 95% | 26.0 ms | 10.0 ms (-16.0) |
| 90% | 26.0 ms | 7.0 ms (-19.0) |
| 85% | 21.0 ms | 5.0 ms (-16.0) |
| 80% | 18.0 ms | 3.0 ms (-15.0) |
| 75% | 15.0 ms | 3.0 ms (-12.0) |
| 50% | 6.0 ms | 2.0 ms (-4.0) |
In both tests timeout on the client was set to 25 ms.
I will deal with this issue in the near future (1-2 weeks), but until then I'm ready to discuss the proposals where this check can be moved or how it can be transformed.