Re: Reduce timing overhead of EXPLAIN ANALYZE using rdtsc?

David Geier <geidav.pg@gmail.com>

From: David Geier <geidav.pg@gmail.com>

To: vignesh C <vignesh21@gmail.com>

Cc: Lukas Fittl <lukas@fittl.com>, Michael Paquier <michael@paquier.xyz>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2023-01-04T12:02:05Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

pg_test_timing: Also test RDTSC[P] timing, report time source, TSC frequency
- 16fca4825483 19 (unreleased) landed
Allow retrieving x86 TSC frequency/flags from CPUID
- bcb2cf41f964 19 (unreleased) landed
instrumentation: Standardize ticks to nanosecond conversion method
- 0022622c93d9 19 (unreleased) landed
instrumentation: Use Time-Stamp Counter on x86-64 to lower overhead
- 294520c44487 19 (unreleased) landed
Zero initialize uses of instr_time about to trigger compiler warnings
- 25b2aba0c3a5 16.0 landed
instr_time: Represent time as an int64 on all platforms
- 03023a2664f8 16.0 landed
Add 250c8ee07ed to git-blame-ignore-revs
- ff23b592ad66 16.0 cited

Attachments

0001-Change-instr_time-to-just-store-nanoseconds-v6.patch (text/x-patch) patch v6-0001
0002-Use-CPU-reference-cycles-via-RDTSC-to-measure-time-v6.patch (text/x-patch) patch v6-0002
0003-Refactor-some-instr_time-related-code-v6.patch (text/x-patch) patch v6-0003

Hi,

> CFBot shows some compilation errors as in [1], please post an updated
> version for the same:
> 09:08:12.525] /usr/bin/ld:
> src/bin/pg_test_timing/pg_test_timing.p/pg_test_timing.c.o: warning:
> relocation against `cycles_to_sec' in read-only section `.text'
> [09:08:12.525] /usr/bin/ld:
> src/bin/pg_test_timing/pg_test_timing.p/pg_test_timing.c.o: in
> function `pg_clock_gettime_ref_cycles':
> [09:08:12.525] /tmp/cirrus-ci-build/build/../src/include/portability/instr_time.h:119:
> undefined reference to `use_rdtsc'
> [09:08:12.525] /usr/bin/ld:
> src/bin/pg_test_timing/pg_test_timing.p/pg_test_timing.c.o: in
> function `test_timing':
> [09:08:12.525] /tmp/cirrus-ci-build/build/../src/bin/pg_test_timing/pg_test_timing.c:135:
> undefined reference to `pg_clock_gettime_initialize_rdtsc'
> [09:08:12.525] /usr/bin/ld:
> /tmp/cirrus-ci-build/build/../src/bin/pg_test_timing/pg_test_timing.c:137:
> undefined reference to `cycles_to_us'
> [09:08:12.525] /usr/bin/ld:
> /tmp/cirrus-ci-build/build/../src/bin/pg_test_timing/pg_test_timing.c:146:
> undefined reference to `cycles_to_us'
> [09:08:12.525] /usr/bin/ld:
> /tmp/cirrus-ci-build/build/../src/bin/pg_test_timing/pg_test_timing.c:169:
> undefined reference to `cycles_to_us'
> [09:08:12.525] /usr/bin/ld:
> /tmp/cirrus-ci-build/build/../src/bin/pg_test_timing/pg_test_timing.c:176:
> undefined reference to `cycles_to_sec'
> [09:08:12.525] /usr/bin/ld: warning: creating DT_TEXTREL in a PIE
> [09:08:12.525] collect2: error: ld returned 1 exit status
>
> [1] - https://cirrus-ci.com/task/5375312565895168
>
> Regards,
> Vignesh

I fixed the compilation error on CFBot.
I missed adding instr_time.c to the Meson makefile.
New patch set attached.

-- 
David Geier
(ServiceNow)