[Enhancement] Enhance performance of ob_wc_mb_utf8mb4 #1593
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gangdeng-intel
changed the title
| r[0] = (unsigned char) w_char; | ||
| } | ||
| else{ | ||
| ret = OB_CS_TOOSMALLN(1); |
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line 1702 and line 1703 should be together, like "} else {", minded that there is empty space around 'else'
| case 4: r[3] = (unsigned char) (0x80 | (w_char & 0x3f)); w_char >>= 6; w_char |= 0x10000; | ||
| case 3: r[2] = (unsigned char) (0x80 | (w_char & 0x3f)); w_char >>= 6; w_char |= 0x800; | ||
| case 2: r[1] = (unsigned char) (0x80 | (w_char & 0x3f)); w_char >>= 6; w_char |= 0xc0; | ||
| case 1: r[0] = (unsigned char) w_char; |
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here, the original logic is when bytes = 4 , it will go through 4 case because there is no 'break', but seems ur modification have different logic.
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Does there any unittest cases?
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Thanks for comment! Right, the logic is different. Will fix it and do more test.
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I fixed the bug in previous commit. Performance improvement is similar as previous submission, because most of characters in Sysbench dataset is ascii.
And I ran unittest of deps/oblib (deps/oblib/unittest/run_tests.sh). There are 2 failures:
18:test_charset
97:test_utility
I think the 2 failures are not caused by this pull request, as the failures are exist even without this PR. @hnwyllmm
Task Description
Enhance performance of function 'ob_wc_mb_utf8mb4'.
When test Oceanbase with Sysbench OLTP_READ_ONLY, ob_wc_mb_utf8mb4 is one of hotspots. It uses ~3.4% CPU time. The line of 'switch (bytes)' uses 57% CPU time of whole function. switch is less efficient due to indirect jump involved.
Solution Description
Eliminating 'switch' by moving related code into 'if/else' can avoid indirect jump and improve performance accordingly. Using Sysbench OLTP_READ_ONLY test, Oceanbase performance can be improved ~2% and percentage of CPU time by ob_wc_mb_utf8mb4 can be reduced from 3.4% to 2.2%.
Passed Regressions
Test manually.
Upgrade Compatibility
N/A
Other Information
N/A
Release Note
N/A