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Linux From Scratch This Forum is for the discussion of LFS.
LFS is a project that provides you with the steps necessary to build your own custom Linux system.

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Old 10-11-2018, 04:59 AM   #16
business_kid
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Quote:
Originally Posted by Jamie Ramone View Post
I'd recommend NEVER doing a make clean on the kernel after the first configure unless there's a good reason and you have a lot of spare time. Rebuilding a kernel from scratch is SLOW, even on modern computers. Also, you don't need the -j option, you can use the MAKEFLAGS environment variable. Setting
Code:
export MAKEFLAGS=j36; make
has the same effect as
Code:
make -j36
;-)
It's not a matter I intend to pursue, but Linus Torvalds wrote the kernel README (Now <kernel-source/Documentation/admin-guide/README.rst) and he recommends a 'make mrproper' as the opening move which is a lot more drastic.

You're right that I can use the MAKEFLAGS, environment variable, but personally I don't, because the odd thing doesn't need or benefit from parallel make jobs. So I like to think about it; if I'm doing a cpu intensive job on the pc while making, I let it run in the background at it's own pace instead of taking over. That mightn't be necessary on more well endowed pcs.
 
Old 10-19-2018, 04:30 PM   #17
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Quote:
Originally Posted by business_kid View Post
It's not a matter I intend to pursue, but Linus Torvalds wrote the kernel README (Now <kernel-source/Documentation/admin-guide/README.rst) and he recommends a 'make mrproper' as the opening move which is a lot more drastic.
Yes, but only for a freshly downloaded kernel, and it's just as slow ;-)

Quote:
You're right that I can use the MAKEFLAGS, environment variable, but personally I don't, because the odd thing doesn't need or benefit from parallel make jobs. So I like to think about it; if I'm doing a cpu intensive job on the pc while making, I let it run in the background at it's own pace instead of taking over. That mightn't be necessary on more well endowed pcs.
Really? I use that with a value of 24 or 36 (I have a PhenomII X6; take a moment, you'll figure it out) and compilation times get cut down drastically! I fail to see how this isn't a benefit. Personal tastes I guess.
 
Old 10-20-2018, 06:10 AM   #18
business_kid
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I've a twin core i3/6G of ram. I tried 'make 'j2,3,4, etc on kernel compiles. Make -j2 sped things up with reference to make -j1; make -j3 just used more ram, but was about the same; make -j4 slowed things down with reference to make -j2.

I'm happy for you with make -j36 cooking your kernel faster. This is a 2013 laptop, probably made in 2012. What would you recommend, and I can leave it running, and try it against make -j2.
 
Old 10-22-2018, 10:50 AM   #19
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I got a PhenomII X6 based desktop...from 2008. With -j36 there are on average 6 processes per core. I set the processor to 2.6 GHz in these cases as well.
 
Old 10-23-2018, 02:10 PM   #20
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Out of curiosity, I did the following test and got the results below for my twin core i3.
Code:
root@RoseViolet:/usr/src/linux-4.14.55# make clean && time make -j2 all > /dev/null 2>&1 &&
> make clean && time make -j12 all > /dev/null 2>&1

#time make -j2:
real	23m49.844s
user	42m50.136s
sys	3m5.274s

#time make -j12 (6 processes per core)
real	24m48.624s
user	45m27.046s
sys	3m9.378s
I've 6 Gig or ram, and checked top briefly. The -j2 had 2 cc1 processes running at 100% or close. I never counted more than 9 cc1 processes on make -j12. They were typically 4-5 @ 15% and the rest doing nothing really (0-5%). The highest I saw was 2 @ 19%. I would allow about 10 secs off the j12 time as I was slowly reading a pdf, but as you see, it's a full minute slower.When you run make -j36, do you see 36 cc1 processes?
 
  


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