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Date:      Sun, 10 May 2020 18:03:27 +0200
From:      Daniel Ebdrup Jensen <debdrup@FreeBSD.org>
To:        hackers@freebsd.org
Subject:   Re: Find specific changes between revisions
Message-ID:  <20200510160327.r5x5j5mkrrcmmy4k@nerd-thinkpad.local>
In-Reply-To: <91d3b015-3708-eacd-3706-5729e0b96e9e@grosbein.net>
References:  <CA%2ByoEx97e=FVH0Ob41cA5RqSFK5_pjG3huWgOEN_e2J1=iB6vA@mail.gmail.com> <bb3a95ba-101a-b874-7919-2f4ad960e049@grosbein.net> <614e0ff9-1adc-1634-5711-ca032d6260bf@fastmail.com> <CA%2ByoEx8if7bKSfHpYi%2BD1iT4xL0sqbw8YzuaPmzzENrmFv_%2BpA@mail.gmail.com> <91d3b015-3708-eacd-3706-5729e0b96e9e@grosbein.net>

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On Sun, May 10, 2020 at 10:41:24PM +0700, Eugene Grosbein wrote:
>10.05.2020 5:52, Mario Lobo wrote:
>
>> The command:
>>
>> svn diff https://svn.freebsd.org/base/stable/11@359971
>> https://svn.freebsd.org/base/stable/11@360676
>>
>> yielded a 170 Mbytes file!!
>>
>> It will be like looking for a needle in a haystack, in the dark, with ju=
st
>> a hunch of where the needle was dropped.
>>
>> Well ... at least I have the haystack.
>>
>> Thanks everyone for the tips!
>
>You don't really need to study source code to bisect the problem,
>just use "svnlite update -rZZZZZ" to move your source tree to the middle p=
oint
>between known working and non-working revisions. Then rebuild and reinstall
>kernel and world, reboot and re-do the test. If it works, you get new (hig=
her)
>working revision and if not, you get new (lower) non-working one.
>
>Repeat until you have only single revision between working and non-working.
>This procedure takes time and effort but this is not like looking for a ne=
edle in a haystack, much easier.
>_______________________________________________
>freebsd-hackers@freebsd.org mailing list
>https://lists.freebsd.org/mailman/listinfo/freebsd-hackers
>To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"

If you're going to be doing this kind of rebuilding from revision to revisi=
on, I=20
feel obliged to mention that you can put MetaMode [1] to great use.

Essentially, it ensures that you only rebuild whatever's changed from one=
=20
revision to another, and on the source tree it can make a HUGE difference w=
hen=20
jumping small revision amounts (and even if large numbers of revisions are=
=20
jumped over, it still has some impact.
It's sort of like ccache, except much more efficient.

Yours,
Daniel Ebdrup Jensen

[1]: https://wiki.freebsd.org/MetaMode

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