It Makes sense, but we can distinguish such code which needs ` CLOCK_MONOTONIC`.
Now I add the configure option `--with-clock-monotonic-coarse`. Michael Paquier <mich...@paquier.xyz> 于2025年3月26日周三 15:34写道： > On Wed, Mar 26, 2025 at 11:14:47AM -0700, 杨江华 wrote: > > This patch modifies the instr_time.h header to prefer > CLOCK_MONOTONIC_COARSE > > when available. By using CLOCK_MONOTONIC_COARSE, we can leverage a lower > > resolution(4ms) but faster alternative for timing operations, which > reduces > > the overhead of frequent timestamp retrievals. This change is expected to > > provide performance improvements, especially in scenarios with frequent > > timing operations. > > > > *Key Changes:* > > > > • *CLOCK_MONOTONIC_COARSE* is used when available, offering faster > > performance with slightly reduced precision. > > > > • For macOS, *CLOCK_MONOTONIC_RAW* remains the preferred choice due to > its > > higher resolution. > > > > • *CLOCK_MONOTONIC* is used as a fallback when neither of the above > options > > is available. > > -#if defined(__darwin__) && defined(CLOCK_MONOTONIC_RAW) > +#ifdef CLOCK_MONOTONIC_COARSE > +#define PG_INSTR_CLOCK CLOCK_MONOTONIC_COARSE > +#elif defined(__darwin__) && defined(CLOCK_MONOTONIC_RAW) > > Why would we want to make this the default? CLOCK_MONOTONIC_COARSE > could show benefits in some code paths. Now, it can also have a > precision of a few milliseconds, and we have a bunch of code paths > that rely on clock_gettime() to be more precise than that so it could > lead to random decisions. You could make that configurable with a > GUC, but it would mean plastering some decision-making in instr_time.h > based on such a GUC, which would likely be annoying performance-wise. > > We are at the end of the v18 development cycle, so it is going to get > some time before you get any review. Good to see that you are > tracking this patch in the commit fest: > https://commitfest.postgresql.org/patch/5669/ > -- > Michael >
0001-Add-optional-support-for-CLOCK_MONOTONIC_COARSE-via-.patch
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