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8202-erts-Add-info-about-used-resolution-for-OS...
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File 8202-erts-Add-info-about-used-resolution-for-OS-monotonic.patch of Package erlang
From 0a1f990d8f9fc1ed948f938e3f9302bcb6c8e63e Mon Sep 17 00:00:00 2001 From: Rickard Green <rickard@erlang.org> Date: Fri, 5 Apr 2024 16:48:54 +0200 Subject: [PATCH 2/2] [erts] Add info about used resolution for OS monotonic time --- erts/doc/src/erlang.xml | 12 ++++++++++++ erts/emulator/beam/erl_time_sup.c | 13 +++++++++++-- erts/emulator/beam/sys.h | 1 + erts/emulator/sys/win32/sys_time.c | 15 +++++++++++---- 4 files changed, 35 insertions(+), 6 deletions(-) diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index a5e4a3b331..51b4c4438e 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -10247,6 +10247,18 @@ Metadata = #{ pid => pid(), however, know that the precision is not better than <c>OsMonotonicTimeResolution</c>.</p> </item> + <tag><c>{used_resolution, UsedOsMonotonicTimeResolution}</c></tag> + <item><p> + The OS monotonic time resolution used by the runtime system. + This is very often the same as <c>OsMonotonicTimeResolution</c>. + However, on some systems the resolution has to be reduced in + order to reliably produce monotonic timestamps. An example of + this is when <c>QueryPerformanceCounter()</c> is used as + OS monotonic time source on Windows. If such a reduction of + the resolution has been done, + <c>UsedOsMonotonicTimeResolution</c> will be smaller than + <c>OsMonotonicTimeResolution</c>. + </p></item> <tag><c>{extended, Extended}</c></tag> <item><p><c>Extended</c> equals <c>yes</c> if the range of time values has been extended; diff --git a/erts/emulator/beam/erl_time_sup.c b/erts/emulator/beam/erl_time_sup.c index 0e1d4b087f..abb945ebd2 100644 --- a/erts/emulator/beam/erl_time_sup.c +++ b/erts/emulator/beam/erl_time_sup.c @@ -93,6 +93,7 @@ struct time_sup_read_only__ { char *os_monotonic_time_clock_id; int os_monotonic_time_locked; Uint64 os_monotonic_time_resolution; + Uint64 os_monotonic_time_used_resolution; Uint64 os_monotonic_time_extended; #endif char *os_system_time_func; @@ -934,6 +935,10 @@ void erts_init_sys_time_sup(void) = sys_init_time_res.os_monotonic_time_info.locked_use; time_sup.r.o.os_monotonic_time_resolution = sys_init_time_res.os_monotonic_time_info.resolution; + time_sup.r.o.os_monotonic_time_used_resolution + = (!sys_init_time_res.os_monotonic_time_info.used_resolution + ? sys_init_time_res.os_monotonic_time_info.resolution + : sys_init_time_res.os_monotonic_time_info.used_resolution); time_sup.r.o.os_monotonic_time_extended = sys_init_time_res.os_monotonic_time_info.extended; #endif @@ -2044,8 +2049,8 @@ bld_monotonic_time_source(Uint **hpp, Uint *szp, Sint64 os_mtime) return NIL; #else int i = 0; - Eterm k[6]; - Eterm v[6]; + Eterm k[7]; + Eterm v[7]; if (time_sup.r.o.os_monotonic_time_disable) return NIL; @@ -2064,6 +2069,10 @@ bld_monotonic_time_source(Uint **hpp, Uint *szp, Sint64 os_mtime) v[i++] = erts_bld_uint64(hpp, szp, time_sup.r.o.os_monotonic_time_resolution); + k[i] = erts_bld_atom(hpp, szp, "used_resolution"); + v[i++] = erts_bld_uint64(hpp, szp, + time_sup.r.o.os_monotonic_time_used_resolution); + k[i] = erts_bld_atom(hpp, szp, "extended"); v[i++] = time_sup.r.o.os_monotonic_time_extended ? am_yes : am_no; diff --git a/erts/emulator/beam/sys.h b/erts/emulator/beam/sys.h index 1ffc7f5028..6a5908d51b 100644 --- a/erts/emulator/beam/sys.h +++ b/erts/emulator/beam/sys.h @@ -727,6 +727,7 @@ typedef struct { ErtsMonotonicTime sys_clock_resolution; struct { Uint64 resolution; + Uint64 used_resolution; char *func; char *clock_id; int locked_use; diff --git a/erts/emulator/sys/win32/sys_time.c b/erts/emulator/sys/win32/sys_time.c index 1febfee829..81e621eb2e 100644 --- a/erts/emulator/sys/win32/sys_time.c +++ b/erts/emulator/sys/win32/sys_time.c @@ -29,8 +29,12 @@ #include "erl_os_monotonic_time_extender.h" #include "erl_time.h" -/* Need to look more closely at qpc before use... */ -#define ERTS_DISABLE_USE_OF_QPC_FOR_MONOTONIC_TIME 1 +/* + * How much to reduce the resolution of the by QueryPerformanceCounter() + * returned values in order to make them monotonic... + */ +#define ERTS_WIN_QPC_SKIP_BITS 10 +#define ERTS_WIN_QPC_SKIP_MASK ((1 << ERTS_WIN_QPC_SKIP_BITS) - 1) #define LL_LITERAL(X) ERTS_I64_LITERAL(X) @@ -159,9 +163,9 @@ os_monotonic_time_qpc(void) if (!(*internal_state.r.o.pQueryPerformanceCounter)(&pc)) erts_exit(ERTS_ABORT_EXIT, "QueryPerformanceCounter() failed\n"); temp = (ErtsMonotonicTime) pc.QuadPart; - } while(!(temp & SKIP)); + } while(!(temp & ERTS_WIN_QPC_SKIP_MASK)); - return temp & (ERTS_I64_LITERAL(0xFFFFFFFFFFFFFFFF)-SKIP); + return temp & (ERTS_I64_LITERAL(0xFFFFFFFFFFFFFFFF)-ERTS_WIN_QPC_SKIP_MASK); } static void @@ -381,6 +385,9 @@ sys_init_time(ErtsSysInitTimeResult *init_resp) time_unit = (ErtsMonotonicTime) pf.QuadPart; internal_state.r.o.using_get_tick_count_time_unit = 0; init_resp->os_monotonic_time_info.resolution = time_unit; + /* We reduce the used resolution in order to make it monotonic... */ + init_resp->os_monotonic_time_info.used_resolution + = time_unit >> ERTS_WIN_QPC_SKIP_BITS; os_mtime_func = os_monotonic_time_qpc; os_times_func = os_times_qpc; } -- 2.35.3
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