[PATCH 0/1] MR10350: server: Cache timezone bias adjustment in set_user_shared_data_time().

[Paul Gofman (＠gofman)]

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10350

[PATCH 1/1] server: Cache timezone bias adjustment in set_user_shared_data_time().

[Paul Gofman]

From: Paul Gofman <[e-mail]>

---
 server/fd.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/server/fd.c b/server/fd.c
index 4c0aa36d359..efb6e8e76b9 100644
--- a/server/fd.c
+++ b/server/fd.c
@@ -379,7 +379,8 @@ static void atomic_store_long(volatile LONG *ptr, LONG value)
 static void set_user_shared_data_time(void)
 {
     timeout_t tick_count = monotonic_time / 10000;
-    static timeout_t last_timezone_update;
+    static timeout_t last_timezone_update, last_timezone_bias = 65535, adjusted_timezone_bias;
+    static int current_year = -1;
     timeout_t timezone_bias;
     struct tm *tm, tm1, tm2;
     time_t now;
@@ -390,13 +391,19 @@ static void set_user_shared_data_time(void)
         tm = gmtime( &now );
         timezone_bias = mktime( tm ) - now;
         tm = localtime( &now );
-        if (tm->tm_isdst)
+        if (current_year != tm->tm_year || last_timezone_bias != timezone_bias)
         {
-            tm1 = tm2 = *tm;
-            tm1.tm_isdst = 0;
-            tm2.tm_isdst = 1;
-            timezone_bias += mktime(&tm1) < mktime(&tm2) ? 3600 : -3600;
+            current_year = tm->tm_year;
+            last_timezone_bias = adjusted_timezone_bias = timezone_bias;
+            if (tm->tm_isdst)
+            {
+                tm1 = tm2 = *tm;
+                tm1.tm_isdst = 0;
+                tm2.tm_isdst = 1;
+                adjusted_timezone_bias += mktime(&tm1) < mktime(&tm2) ? 3600 : -3600;
+            }
         }
+        timezone_bias = adjusted_timezone_bias;
         timezone_bias *= TICKS_PER_SEC;
 
         atomic_store_long(&user_shared_data->TimeZoneBias.High2Time, timezone_bias >> 32);
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10350

[Paul Gofman (＠gofman)]

As discovered in https://gitlab.winehq.org/wine/wine/-/merge_requests/10348 / https://bugs.winehq.org/show_bug.cgi?id=59514 , mktime() with switched tm_isdst takes a long time to execute. This patch introduces the same logic as in ntdll's get_timezone_info() to guess that timezone / timezone bias has not changed and avoids the expensive adjustment in this case.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10350#note_132377