From: "Martin Liška" <mliska@suse.cz>
To: Jan Hubicka <hubicka@ucw.cz>,
Richard Biener <richard.guenther@gmail.com>
Cc: Jakub Jelinek <jakub@redhat.com>, Jeff Law <law@redhat.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Michael Matz <matz@suse.de>
Subject: Re: [PATCH] Properly detect working jobserver in gcc driver.
Date: Fri, 02 Aug 2019 09:19:00 -0000 [thread overview]
Message-ID: <0221cd30-5ce4-624f-afe5-15525092821a@suse.cz> (raw)
In-Reply-To: <20190802091543.spbiwrpkfgmc3wil@kam.mff.cuni.cz>
On 8/2/19 11:15 AM, Jan Hubicka wrote:
>> On Fri, Aug 2, 2019 at 10:50 AM Jakub Jelinek <jakub@redhat.com> wrote:
>>>
>>> On Fri, Aug 02, 2019 at 10:47:10AM +0200, Martin Liška wrote:
>>>>> Can you strace if other fds are opened and not closed in the spot you had it
>>>>> before? Advantage of doing it there is that it will not be done for all the
>>>>> -E/-S/-c compilations when the linker is not spawned.
>>>>
>>>> I've used the same trick which you used and I'm attaching the output.
>>>> I believe it's fine, I can't see any opened fd by GCC.
>>>
>>> LGTM.
>>
Hi.
>> Btw, we discussed yesterday on the phone and the conclusion was to
>> make -flto auto-detect a job-server (but not fall back to # of threads)
>> and add -flto=auto to auto-detect a job-server and fall back to # of threads.
>> That basically makes -flto=jobserver the default behavior which means
>> we should document -flto=1 as a way to override jobserver detection.
>
> And concerning to the yesterday discussion, my preference would still be
> -flto to first try presence of jobserver and default to number of
> threads otherwise. It seems like user friendly default to me and other
> tools with reasonable parallelism support usually behaves this way, too.
I also like the default as Honza defined.
>
> Sure one can use -flto=auto everywhere but then one needs to use
> different options for differnt compilers. It would be nice to make
> -flto to do right hting for majority of users including those like me
> who cut&paste command lines from Make output and execute them by hand.
Note that our ambition is to ideally backport the patches to our gcc9 package.
The auto-detection of job-server with -flto is a behavior change that will happen
in the gcc9 package.
To be honest I don't like the invention of 'auto' value for -flto command.
That would be useful just for gcc9 right now :/
Martin
>
> The fork bombing is IMO relatively rare and it was not what Jakub ran
> into (it was broken jobserv detection).
> After all whole distro built with Martin's orriginal approach of
> -flto=<nthreads> which forkbombs on every possible occasion.
>
> Said that, I could live with more conservative defaults.
> Honza
>
next prev parent reply other threads:[~2019-08-02 9:19 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 8:55 [PATCH] Come up with -flto=auto option Martin Liška
2019-07-23 9:29 ` Jan Hubicka
2019-07-23 10:34 ` [PATCH] Deduce automatically number of cores for -flto option Martin Liška
2019-07-24 15:47 ` Jeff Law
2019-07-29 13:37 ` Martin Liška
2019-07-30 13:47 ` Martin Liška
2019-07-31 1:23 ` Jakub Jelinek
2019-07-31 7:24 ` Martin Liška
2019-07-31 7:40 ` Jakub Jelinek
2019-07-31 7:49 ` Jan Hubicka
2019-07-31 7:50 ` Martin Liška
2019-07-31 7:54 ` Martin Liška
2019-07-31 8:08 ` Jakub Jelinek
2019-07-31 8:21 ` Jan Hubicka
2019-07-31 8:37 ` Martin Liška
2019-07-31 9:12 ` Jakub Jelinek
2019-07-31 9:15 ` Jan Hubicka
2019-07-31 9:17 ` Jakub Jelinek
2019-07-31 9:22 ` Jan Hubicka
2019-07-31 10:02 ` Martin Liška
2019-07-31 12:02 ` Jan Hubicka
2019-07-31 15:42 ` Martin Liška
2019-08-01 13:19 ` Jakub Jelinek
2019-08-01 14:34 ` [PATCH] Properly detect working jobserver in gcc driver Martin Liška
2019-08-01 14:41 ` Jakub Jelinek
2019-08-02 6:30 ` Martin Liška
2019-08-02 7:45 ` Jakub Jelinek
2019-08-02 8:47 ` Martin Liška
2019-08-02 8:50 ` Jakub Jelinek
2019-08-02 9:04 ` Richard Biener
2019-08-02 9:08 ` Jan Hubicka
2019-08-02 9:15 ` Jan Hubicka
2019-08-02 9:19 ` Martin Liška [this message]
2019-08-02 9:55 ` Richard Biener
2019-08-05 6:41 ` Martin Liška
2019-08-09 8:14 ` Martin Liška
2019-08-09 8:22 ` Richard Biener
2019-08-09 12:51 ` Martin Liška
2019-08-09 13:56 ` Martin Liška
2019-08-12 15:18 ` Jeff Law
2019-07-23 13:13 ` [PATCH] Come up with -flto=auto option Jeff Law
2019-07-23 13:22 ` Richard Biener
2019-07-23 13:57 ` Michael Matz
2019-07-23 14:00 ` Jeff Law
2019-07-23 14:27 ` Martin Liška
2019-07-23 22:56 ` Jeff Law
2019-07-24 6:59 ` Martin Liška
2019-07-24 15:16 ` Jeff Law
2019-07-23 22:32 ` Allan Sandfeld Jensen
2019-07-24 6:47 ` Martin Liška
2019-07-24 7:12 ` Allan Sandfeld Jensen
2019-07-24 7:15 ` Martin Liška
2019-07-24 11:09 ` Nathan Sidwell
2019-07-24 15:46 ` Jeff Law
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