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mek42
n00b
Joined: 18 Feb 2015
Posts: 12
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 Posted: Fri Feb 20, 2015 2:21 am Post subject: prospective new user / compiler choice |
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I have ordered parts for a new system. Have just about decided to give Gentoo a spin. Doing some pre-reading had shown me how little I know.
One question I have is whether people have used something other than gcc to compile their system. Would an Opteron madhine benefit from using the AMD compiler to make the system? |
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dol-sen
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Joined: 30 Jun 2002
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Location: Richmond, BC, Canada
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| Posted: Fri Feb 20, 2015 4:49 am Post subject: |
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For modern hardware, it comes down to whether you NEED the absolute speed for intense mathimatical calculations that run days, weeks, months, or for normal desktop activities.
First, let me point out that most software is tested using gcc and the standard linker. So, if this is your first Gentoo install, stick with gcc, it will make life easier for you. You have a lot more to learn doing the install, configuring and maintaining your system. Besides, for normal desktop activities, it is unlikely that you will notice any speed difference. Getting an SSD instead of a regular HDD will make a far bigger speed improvement than a compiler will ever make.
Once you are comfortable with your system, you can install a different compiler alongside gcc and begin some testing. You will undoubtedly run into issues with compiling some applications with compilers other than gcc.
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Brian
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steveL
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| Posted: Fri Feb 20, 2015 8:09 am Post subject: |
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| What dol-sen said; stick with gcc. |
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Irre
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Joined: 09 Nov 2013
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Location: Stockholm
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| Posted: Fri Feb 20, 2015 8:52 am Post subject: |
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| I think clang (llvm.org) is a good choice. It is faster than gcc. FreeBSD prefer it to gcc. I think we should switch too. |
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Naib
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| Posted: Fri Feb 20, 2015 8:59 am Post subject: |
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| Irre wrote: | | I think clang (llvm.org) is a good choice. It is faster than gcc. FreeBSD prefer it to gcc. I think we should switch too. |
faster maybe but how proven? Especially against the entire tree.
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Yamakuzure
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Joined: 21 Jun 2006
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Location: Adendorf, Germany
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| Posted: Fri Feb 20, 2015 10:20 am Post subject: |
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| Naib wrote: | | Irre wrote: | | I think clang (llvm.org) is a good choice. It is faster than gcc. FreeBSD prefer it to gcc. I think we should switch too. |
faster maybe but how proven? Especially against the entire tree. |
Rumors say it is now slower. However, the performance of the binaries is (and was always) worse. So why reduce compile time if this affects overall system performance negatively? Phoronix is full of tests regarding clang versus gcc. (Example: GCC 4.9 vs. LLVM Clang 3.5, google for "Phoronix clang vs gcc" to find many more.)
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mek42
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Joined: 18 Feb 2015
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| Posted: Fri Feb 20, 2015 11:30 am Post subject: |
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Ok, I'll stick with gcc for most things, maybe experiment with compilers for compute intensive applications - for my uses panoramic stitching (photography) comes to mind.
I'm going to have two 128 Gb SATA SSD drives and two 450 Gb SAS 15K near-line drives, each pair in RAID 1. I've started reading about howto partition between these two drives. It looks like SSD should get /boot and /, maybe separate out /usr and /opt on separate SSD partitions, using only 3/4 available space. Then on the 15K drive I'll have /home, /var, /tmp and swap. This is a desktop machine, but if I likeGentoo I'll also put it on laptop, so I think I'm going to make swap a little bigger than total RAM to configure hibernate.
If I have binaries in ~/bin would there be an advantage with making /usr/username directory and making ~/bin be a symbolic link to /usr/username?
Also, /etc is going to have lots of small text files. Should that go on the 15k drive as well? |
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augustin
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| Posted: Mon Feb 23, 2015 9:58 pm Post subject: |
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| mek42 wrote: |
I'm going to have two 128 Gb SATA SSD drives and two 450 Gb SAS 15K near-line drives, each pair in RAID 1. |
Hi mek,
I'm also a very soon to be new user. I am preparing to build a new box in the next month or two. I am currently pondering what storage choice to make (spacious HDD vs rapid SSD vs SAS + RAID). I am very interested in your make up, quoted above. Can you share with us the reasoning that led you to such a choice? Had you considered other options?
Thanks and good luck on your new build!
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NeddySeagoon
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| Posted: Mon Feb 23, 2015 10:31 pm Post subject: |
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mek42,
/etc is a directory on /. Your boot sequence will die a horrible death if its elsewhere.
After / is mounted, /etc/fstab is read to find out what else to mount ... but it can't be read as /etc is no longer on /
There are other things too.
Will you really need /tmp on disk?
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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mek42
n00b
Joined: 18 Feb 2015
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| Posted: Wed Feb 25, 2015 2:48 pm Post subject: |
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| augustin wrote: | | mek42 wrote: |
I'm going to have two 128 Gb SATA SSD drives and two 450 Gb SAS 15K near-line drives, each pair in RAID 1. |
Hi mek,
I'm also a very soon to be new user. I am preparing to build a new box in the next month or two. I am currently pondering what storage choice to make (spacious HDD vs rapid SSD vs SAS + RAID). I am very interested in your make up, quoted above. Can you share with us the reasoning that led you to such a choice? Had you considered other options?
Thanks and good luck on your new build!
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To be honest, I purchased based on reading about consumer grade builds, not considering that I'm making, in effect, a server/workstation class machine. With what I now know about filesystems and partitioning I think things will have been easier for me if I'd just gotten 4 300 Gb 15krpm SAS drives to do a mirror of stripes. Oh well, this will force me to learn more.
They say an ssd drive is 2-3 times faster than a consumer grade 7200 rpm SATA hdd. A 15krpm SAS hdd should be just over twice as fast as the SATA comparison drive, so I don't know that the performance boost of ssd in my system is going to justify the time I'm spending figuring things out for install. At least it is a hobby machine and I will be walking away with a little bit more admin knowledge. |
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mek42
n00b
Joined: 18 Feb 2015
Posts: 12
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| Posted: Wed Feb 25, 2015 2:50 pm Post subject: |
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| NeddySeagoon wrote: | mek42,
/etc is a directory on /. Your boot sequence will die a horrible death if its elsewhere.
After / is mounted, /etc/fstab is read to find out what else to mount ... but it can't be read as /etc is no longer on /
There are other things too.
Will you really need /tmp on disk? |
I didn't know that /tmp was by default in RAM, thank you.
As for which devices the various root directories are in, isn't that what the initramdisk is for? |
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mrbassie
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Joined: 31 May 2013
Posts: 772
Location: over here
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| Posted: Wed Feb 25, 2015 5:18 pm Post subject: |
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| Irre wrote: | | I think clang (llvm.org) is a good choice. It is faster than gcc. FreeBSD prefer it to gcc. I think we should switch too. |
They prefer anything that isn't GPL'd though tbf.
I'm sure I read the other day somewhere that while clang compiles more quickly the resultant binaries are slower. |
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augustin
Guru
Joined: 23 Feb 2015
Posts: 318
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| Posted: Wed Feb 25, 2015 5:38 pm Post subject: |
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| mek42 wrote: |
To be honest, I purchased based on reading about consumer grade builds, not considering that I'm making, in effect, a server/workstation class machine. With what I now know about filesystems and partitioning I think things will have been easier for me if I'd just gotten 4 300 Gb 15krpm SAS drives to do a mirror of stripes. Oh well, this will force me to learn more.
They say an ssd drive is 2-3 times faster than a consumer grade 7200 rpm SATA hdd. A 15krpm SAS hdd should be just over twice as fast as the SATA comparison drive, so I don't know that the performance boost of ssd in my system is going to justify the time I'm spending figuring things out for install. At least it is a hobby machine and I will be walking away with a little bit more admin knowledge. |
Interesting. Thanks for the feedback. I am still considering options for my own build. Best of luck with yours. |
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NeddySeagoon
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Joined: 05 Jul 2003
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Location: 56N 3W
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| Posted: Wed Feb 25, 2015 7:30 pm Post subject: |
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mek42,
/tmp can be in RAM but its not by default. Its no longer persistent, as its flushed by the init scripts.
| mek42 wrote: | | As for which devices the various root directories are in, isn't that what the initramdisk is for? |
Not really, no. The initramdisk is a fake root filesystem, used to house user space tools needed to be run before the real root filesystem is mounted.
Thats things like starting raid, lvm, decrypting roof.
I suppose your init script could mount root and /etc, just as it can mount root and /usr and anything else you fancy.
It would be unusual.
I'm not sure where you get your speed figures from for rotating rust. They are possibly correct for sustained sequential reads but thats not a real world use case.
You need to factor in track seek (track to track) and track latency (1/2 a rotation) times before you even get to start reading. For SSDs these times are between zero and negligible.
This is what gives SSDs their much higher real world speed increase over rotating rust.
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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