RFR(S): 8241638: launcher time metrics alway report 1 on Linux when _JAVA_LAUNCHER_DEBUG set(Internet mail)
linzang at tencent.com
Tue Mar 31 02:39:21 UTC 2020
Hi David, Henry, Alan,
Thanks a lot for your review.
I have considered use clock_gettime() first, but I seached the code and found there is a marco SUPPORTS_CLOCK_MONOTONIC guard the usage of it. Which makes me think it may not be available under specific situation. So I choosed gettimeofday.
Do you think the patch need to be refined to remove HAVE_GETHRTIME as Alan suggested? Thanks.
>On 2020/3/31, 8:05 AM, "David Holmes" <david.holmes at oracle.com> wrote:
> On 31/03/2020 4:08 am, Henry Jen wrote:
> > Based on my understanding to gethrtime(), the main benefit is not to be affected by settimeofday or adjtime. I think it is probably better to use
> > clock_gettime(CLOCK_MONOTONIC_RAW, ts);
> > which I checked seems to be available on both Linux and Mac. Haven’t test it though.
> Not guaranteed to be available - either clock_gettime function or that
> particular clock - at build time or runtime. We use a check in the build
> system to determine build-time availability for hotspot, and then use
> dl_lookup etc at runtime to determine if actually available. We should
> be able to get rid of this one day but we checked fairly recently and
> there were still some issues.
> gettimeofday is a lot better than returning 1. Otherwise call into the
> VM and use JVM_NanoTime.
> > Cheers,
> > Henry
> >> On Mar 30, 2020, at 1:37 AM, Alan Bateman <Alan.Bateman at oracle.com> wrote:
> >> On 30/03/2020 03:41, linzang(臧琳) wrote:
> >>> Dear All,
> >>> May I ask your help to reivew this tiny patch? Thanks.
> >>> BRs,
> >>> Lin
> >>> From: "linzang(臧琳)" <linzang at tencent.com>
> >>> Date: Thursday, March 26, 2020 at 3:13 PM
> >>> To: "core-libs-dev at openjdk.java.net" <core-libs-dev at openjdk.java.net>
> >>> Subject: RFR(S): 8241638: launcher time metrics alway report 1 on Linux when _JAVA_LAUNCHER_DEBUG set
> >>> Dear All,
> >>> May I ask your help to review this tiny fix?
> >>> Bug: https://bugs.openjdk.java.net/browse/JDK-8241638
> >>> Webrev: http://cr.openjdk.java.net/~lzang/8241638/webrev01/
> >>> Thanks!
> >> Using gettimeofday on non-Solaris platforms seems reasonable here. The comment in the patch suggests Linux but it's other Unix builds too. Also just a minor nit that the code in java.base uses 4-space indent, not 2. Looking at the patch makes me wondering if we should remove HAVE_GETHRTIME as it seems to be only used on Solaris >and the launcher is already using #ifdef __solaris__ in several places. Henry, do you have any comments on this?
> >> -Alan
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