From 4d7a6d04b2c71aabb9d6e619f4405887806a5be8 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Sun, 1 Dec 2019 16:21:05 +0000 Subject: Avoid unnecessary tzset() call Akatsuki reported ENV['TZ'] = 'UTC' improved 7x-8x faster on following code. t = Time.now; 100000.times { Time.new(2019) }; Time.now - t https://hackerslab.aktsk.jp/2019/12/01/141551 commit 4bc1669127(reduce tzset) dramatically improved this situation. But still, TZ=UTC is faster than default. This patch removs unnecessary tzset() call completely. Performance check ---------------------- test program: t = Time.now; 100000.times { Time.new(2019) }; Time.now - t before: 0.387sec before(w/ TZ): 0.197sec after: 0.162sec after(w/ TZ): 0.165sec OK. Now, Time creation 2x faster *and* TZ=UTC doesn't improve anything. We can forget this hack completely. :) Side note: This patch slightly changes Time.new(t) behavior implicitly. Before this patch, it might changes default timezone implicitly. But after this patch, it doesn't. You need to reset TZ (I mean ENV['TZ'] = nil) explicitly. But I don't think this is big impact. Don't try to change /etc/localtime on runtime. Side note2: following test might be useful for testing "ENV['TZ'] = nil". ----------------------------------------- % cat <<'End' | sudo sh -s rm -f /etc/localtime-; cp -a /etc/localtime /etc/localtime- rm /etc/localtime; ln -s /usr/share/zoneinfo/Asia/Tokyo /etc/localtime ./ruby -e ' p Time.new(2000).zone # JST File.unlink("/etc/localtime"); File.symlink("/usr/share/zoneinfo/America/Los_Angeles", "/etc/localtime") p Time.new(2000).zone # JST (ruby does not follow /etc/localtime modification automatically) ENV["TZ"] = nil p Time.new(2000).zone # PST (ruby detect /etc/localtime modification) ' rm /etc/localtime; cp -a /etc/localtime- /etc/localtime; rm /etc/localtime- End --- time.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) (limited to 'time.c') diff --git a/time.c b/time.c index 3cb5a060f9..137d5e0f9f 100644 --- a/time.c +++ b/time.c @@ -3139,15 +3139,10 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp) find_dst = 0 < tptr->tm_isdst; -#if defined(HAVE_MKTIME) - tm0 = *tptr; - if (!utc_p && (guess = mktime(&tm0)) != -1) { - tm = GUESS(&guess); - if (tm && tmcmp(tptr, tm) == 0) { - goto found; - } + /* /etc/localtime might be changed. reload it. */ + if (!ruby_tz_uptodate_p) { + tzset(); } -#endif tm0 = *tptr; if (tm0.tm_mon < 0) { -- cgit v1.2.3