Hi, For decades there has always been a warning not to do parallel builds of the kernel or the world (Linux kernel builds also suggest not to do this). Every once in a while, I see people post about 5 minutes. This only way I can see this happening is by doing a parallel build (-j 16 on a Xeon Monster box). Are parallel builds safe? If not, what are actual risk factors and can they be mitigated? Walter -- The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding. -- Justice Louis D. Brandeis
On Sun, 22 Jan 2017 22:57:46 -0800 Walter Parker <walterp at gmail.com> wrote:> For decades there has always been a warning not to do parallel builds of > the kernel or the world (Linux kernel builds also suggest not to do this). > > Every once in a while, I see people post about 5 minutes. This only way I > can see this happening is by doing a parallel build (-j 16 on a Xeon > Monster box). > > Are parallel builds safe? If not, what are actual risk factors and can they > be mitigated?Not only do I use -j, I also use ccache. Another option is to use WITH_META_MODE=YES, that's where most of the 5-minute reports come from, I imagine. I haven't used it myself. My kernel takes 10 minutes with world taking about two hours. I generally just leave them building overnight. The risks of parallel builds are mostly in the past, concurrency was still just coming out and there were chances that something would get compiled before it's dependency, breaking your compile and wasting all of those hours. Cheers, -- Sergei Akhmatdinov My GPG public key: gpg --keyserver pgp.mit.edu --recv-keys AD800D99 -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 833 bytes Desc: OpenPGP digital signature URL: <http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20170123/ef95bfc5/attachment.sig>
On 23/01/2017 06:57, Walter Parker wrote:> Hi, > > For decades there has always been a warning not to do parallel builds of > the kernel or the world (Linux kernel builds also suggest not to do this). > > Every once in a while, I see people post about 5 minutes. This only way I > can see this happening is by doing a parallel build (-j 16 on a Xeon > Monster box). > > Are parallel builds safe? If not, what are actual risk factors and can they > be mitigated?I remember warnings to the effect that while buildworld and buildkernel was safe, installworld and installkernel were not. I use -j32 on i7 monster boxes. -- J.
Walter Parker <walterp at gmail.com> writes:> For decades there has always been a warning not to do parallel builds of > the kernel or the world (Linux kernel builds also suggest not to do this). > > Every once in a while, I see people post about 5 minutes. This only way I > can see this happening is by doing a parallel build (-j 16 on a Xeon > Monster box). > > Are parallel builds safe? If not, what are actual risk factors and can they > be mitigated?As a general rule, it's safe. But don't report failures from a parallel build. This is not so much an issue of parallel builds being unsupported as of the logs being harder to read.