Re: Moving from a 686-pae kernel to amd64?
If you are starting with a clean disk, do not use the installer's partitioning scheme. Problematic at best. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/2555858.GjuxXJF5l1@dovidhalevi
Re: Moving from a 686-pae kernel to amd64?
Bob Proulx a écrit : Sharon Kimble wrote: This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? How much memory do you have in your system? If the answer is 4G or less then there is no advantage. Stay with the 32-bit kernel. If the answer is 64G or more then yes you should definitely use a 64-bit kernel. If the answer is between 4G and 64G then the answer is it depends and there are advantages and disadvantages to both. A 64-bit kernel won't have much advantage for a 32-bit userspace. Quote for the kernel source : Linux can use up to 64 Gigabytes of physical memory on x86 systems. However, the address space of 32-bit x86 processors is only 4 Gigabytes large. That means that, if you have a large amount of physical memory, not all of it can be permanently mapped by the kernel. The physical memory that's not permanently mapped is called high memory. If the address range available to the kernel is less than the physical memory installed, the remaining memory will be available as high memory. Accessing high memory is a little more costly than low memory, as it needs to be mapped into the kernel first. By default, a 32-bit kernel splits the 4 GiB address space in 1 GiB for low memory and 3 GiB for user address space. So all physical memory above 1 GiB (high memory) cannot be permanently mapped, and each user process has a usable virtual address space of 3 GiB. IIRC, a 64-bit kernel gets rid of the memory split, which has two advantages : - all physical memory is mapped permanently, no more low/high memory above 1 GiB - 32-bit user processes have a usable virtual address space of 4 GiB instead of 3 GiB. So I guess that memory intensive 32-bit applications could take advantage of a 64-bit kernel. Is your web browser exceeding 3G of ram image? Is this possible with a 32-bit kernel ? -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/54f2f140.3040...@plouf.fr.eu.org
Re: Moving from a 686-pae kernel to amd64?
Pascal Hambourg wrote: Bob Proulx a écrit : A 64-bit kernel won't have much advantage for a 32-bit userspace. Quote for the kernel source : Linux can use up to 64 Gigabytes of physical memory on x86 systems. However, the address space of 32-bit x86 processors is only 4 Gigabytes large. That means that, if you have a large amount of physical memory, not all of it can be permanently mapped by the kernel. The physical memory that's not permanently mapped is called high memory. If the address range available to the kernel is less than the physical memory installed, the remaining memory will be available as high memory. Accessing high memory is a little more costly than low memory, as it needs to be mapped into the kernel first. By default, a 32-bit kernel splits the 4 GiB address space in 1 GiB for low memory and 3 GiB for user address space. So all physical memory above 1 GiB (high memory) cannot be permanently mapped, and each user process has a usable virtual address space of 3 GiB. Yes. As stated accessing this extra memory space will require remapping the page registers. Basically it causes a page fault and the kernel page fault handler will remap the pages to allow access to the newly accessed pages of memory. This causes the access to be slower because it must trigger a page fault first and the kernel must remap the pages. But that won't happen all of the time. Usually you would only have one program that is using a large amount of memory. If that is a 32-bit program then it is limited to 3G of memory. There is a 3G limit per process for 32-bit programs. Therefore no 32-bit program is going to use more than 3G. Therefore, say, in an 8G ram system no single program can thrash the 8G system memory. It may cause other programs pages to be remapped out but after having done so then the large 3G program would usually stay mapped. Of course if you were running two or more large 3G programs on an 8G ram system with a 32-bit PAE kernel and both of them were running then each of them would be page faulting and remapping out the other's pages. But all of the pages stay in ram. This isn't a classic thrash of VM to swap. No disk is involved. All of the pages are in ram. It is just the kernel page map tables that get remapped. So pretty fast. But still a page fault trap and handle when it needs to be remapped. So not completely without cost. Every so often instead of a fast ram access it causes a page trap and handle to fixup the access. Performance is easy to guess at but hard to guess correctly. Things we think will have a high performance change tend not to be so large. Things we think won't make a difference tends to make a bigger difference. This is why objective benchmarks are really the only way to measure it. And benchmarks are small little snapshot views which is why we have so many different ways to benchmark. Also a 32-bit system can install a 64-bit kernel. But all of the application userland would still be 32-bit. In order to really have advantage the kernel and the userland both would need to be converted to 64-bit. If someone had already installed a 32-bit system then installing the 64-bit kernel is easy and trouble free. Go for it. But I don't think it is necessary to reinstall the system to get a 64-bit userland just for having it. However not having a 64-bit userland means the benefits of the 64-bit kernel are limited. IIRC, a 64-bit kernel gets rid of the memory split, which has two advantages : - all physical memory is mapped permanently, no more low/high memory above 1 GiB Yes! Exactly. Since the 64-bit kernel can directly access all of the ram without secondary page registers it doesn't ever need the page fault trap handle to remap the PAE page registers. Instead it simply uses a flat address space for all memory. The performance penalty of the 32-bit PAE kernel when it needs to remap pages is gone. It was only a small penalty and only triggered when running multiple processes however. This performance difference is not typically noticeable by a desktop user. Scientific and engineering users running compute tasks in a compute farm are the ones who will mostly notice the difference. - 32-bit user processes have a usable virtual address space of 4 GiB instead of 3 GiB. So I guess that memory intensive 32-bit applications could take advantage of a 64-bit kernel. Yes. We used to do that all of the time. The actual number number is just short of 4G. A 32-bit test program that malloc()'s 1M of memory in a loop will be able to malloc() 3056M of memory on a 32-bit kernel but 3803M of memory on a 64-bit kernel. The 64-bit kernel allows the 32-bit program to have 747M more space. Again desktop users will be unlikely to notice this capability difference. Scientific and engineering users often need to run large memory programs that have grown above 3G of memory space required. Being able to get a little bit
Re: Moving from a 686-pae kernel to amd64?
On Saturday 28 February 2015 20:57:04 Sharon Kimble wrote: I installed this jessie setup on 10/02/14 from an old wheezy net-install disc dated 28/05/13! I'm in the process of downloading a jessie net-install for future installation. This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? And if it is a good idea, It is not. how do I do it? Is it as simple as downloading the 3.16.0-4-amd64 kernel, reboot to it, and delete the 3.16.0-4-686-pae kernel? Thanks Sharon. Yes, it is as easy as this to run into all kinds of problems. This question has been asked before on this list and the answer is: Provided you got the 64bit hardware, reinstall a complete amd64 system. If you need to install certain 32bit programs you will want to read up on multiarch: https://www.debian-administration.org/article/531/Using_proprietary_i386_apps_on_an_amd64_system Here are some words about a transition from i386 to amd64 but if you ask my opinion: far too much hassle - it's at least not worth my time. https://www.v13.gr/blog/?p=11 If you can't afford to spend the time to reinstall completely right now, then stay with i386 until you can invest the time for a shiny new system. Sincerely Eike -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/2727337.TdZh5lkGGm@lxcl01
Re: Moving from a 686-pae kernel to amd64?
My new toshiba is a 64 bit amd system. It has 6G of memory and 750G hard drive. Is the 64 bit system better or should I install the 32 bit. I am using weezy. Moe On 02/28/2015 05:05 PM, Bob Proulx wrote: Sharon Kimble wrote: This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? How much memory do you have in your system? If the answer is 4G or less then there is no advantage. Stay with the 32-bit kernel. If the answer is 64G or more then yes you should definitely use a 64-bit kernel. If the answer is between 4G and 64G then the answer is it depends and there are advantages and disadvantages to both. If you currently have a 32-bit system then I recommend staying there. A 64-bit kernel won't have much advantage for a 32-bit userspace. It is rather a pain to change from 32-bit userland to 64-bit. Not really worth it. Is your web browser exceeding 3G of ram image? If the answer is yes then you should re-install to a 64-bit userland. If the answer is no then stick with 32-bits. And if it is a good idea, how do I do it? Is it as simple as downloading the 3.16.0-4-amd64 kernel, reboot to it, and delete the 3.16.0-4-686-pae kernel? Simply install the linux-image-amd64 metapackage, let it drag in the version numbered kernel, and then reboot to it. # uname -a Linux joseki 3.2.0-4-686-pae #1 SMP Debian 3.2.65-1+deb7u2 i686 GNU/Linux # apt-get install linux-image-amd64 Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: linux-image-3.2.0-4-amd64 Suggested packages: linux-doc-3.2 debian-kernel-handbook The following NEW packages will be installed: linux-image-3.2.0-4-amd64 linux-image-amd64 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 23.4 MB of archives. After this operation, 105 MB of additional disk space will be used. Do you want to continue [Y/n]? Bob -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/54f24045.8050...@tampabay.rr.com
Moving from a 686-pae kernel to amd64?
I installed this jessie setup on 10/02/14 from an old wheezy net-install disc dated 28/05/13! I'm in the process of downloading a jessie net-install for future installation. This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? And if it is a good idea, how do I do it? Is it as simple as downloading the 3.16.0-4-amd64 kernel, reboot to it, and delete the 3.16.0-4-686-pae kernel? Thanks Sharon. -- A taste of linux = http://www.sharons.org.uk my git repo = https://bitbucket.org/boudiccas/dots TGmeds = http://www.tgmeds.org.uk Debian testing, fluxbox 1.3.6, emacs 24.4.1.0 signature.asc Description: PGP signature
Re: Moving from a 686-pae kernel to amd64?
Sorry, I meant that I installed this jessie setup on 10/02/15! Got the year wrong! Ooops! Sharon. -- A taste of linux = http://www.sharons.org.uk my git repo = https://bitbucket.org/boudiccas/dots TGmeds = http://www.tgmeds.org.uk Debian testing, fluxbox 1.3.6, emacs 24.4.1.0 signature.asc Description: PGP signature
Re: Moving from a 686-pae kernel to amd64?
Linux-Fan wrote: Maureen L Thomas wrote: My new toshiba is a 64 bit amd system. It has 6G of memory and 750G hard drive. Is the 64 bit system better or should I install the 32 bit. I am using weezy. I recommend you to install the 64 bit version so that a single process is able to address more than two GiB of RAM (can be useful with data compression like 7z and other software which can make use a lot of RAM). Agreed. 6G and a pristine new system install then I would install an amd64 64-bit system. Actually even with 4G I usually install 64-bit anyway just for consistency with the new direction everything is moving. But as you can see I do still have 32-bit systems and I am not converting them to 64-bit as a conversion. Bob signature.asc Description: Digital signature
Re: Moving from a 686-pae kernel to amd64?
Sharon Kimble wrote: This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? How much memory do you have in your system? If the answer is 4G or less then there is no advantage. Stay with the 32-bit kernel. If the answer is 64G or more then yes you should definitely use a 64-bit kernel. If the answer is between 4G and 64G then the answer is it depends and there are advantages and disadvantages to both. If you currently have a 32-bit system then I recommend staying there. A 64-bit kernel won't have much advantage for a 32-bit userspace. It is rather a pain to change from 32-bit userland to 64-bit. Not really worth it. Is your web browser exceeding 3G of ram image? If the answer is yes then you should re-install to a 64-bit userland. If the answer is no then stick with 32-bits. And if it is a good idea, how do I do it? Is it as simple as downloading the 3.16.0-4-amd64 kernel, reboot to it, and delete the 3.16.0-4-686-pae kernel? Simply install the linux-image-amd64 metapackage, let it drag in the version numbered kernel, and then reboot to it. # uname -a Linux joseki 3.2.0-4-686-pae #1 SMP Debian 3.2.65-1+deb7u2 i686 GNU/Linux # apt-get install linux-image-amd64 Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: linux-image-3.2.0-4-amd64 Suggested packages: linux-doc-3.2 debian-kernel-handbook The following NEW packages will be installed: linux-image-3.2.0-4-amd64 linux-image-amd64 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 23.4 MB of archives. After this operation, 105 MB of additional disk space will be used. Do you want to continue [Y/n]? Bob signature.asc Description: Digital signature
Re: Moving from a 686-pae kernel to amd64?
On 02/28/2015 11:25 PM, Maureen L Thomas wrote: My new toshiba is a 64 bit amd system. It has 6G of memory and 750G hard drive. Is the 64 bit system better or should I install the 32 bit. I am using weezy. Moe I recommend you to install the 64 bit version so that a single process is able to address more than two GiB of RAM (can be useful with data compression like 7z and other software which can make use a lot of RAM). HTH Linux-Fan -- http://masysma.lima-city.de/ signature.asc Description: OpenPGP digital signature
Re: Moving from a 686-pae kernel to amd64?
I did exactly that several years ago with no problem. I installed an amd64 kernel at which point grub knew about both. Changed default boot to the new kernel and ran for a while. Once all was well I uninstalled the pae kernel. I did it mostly because I expect that amd64 is the dominant kernel in the future. Although I haven't needed to, I believe I could add 64 bits as a foreign architecture if I wanted to run a 64 bit process. What appears to be too hard to contemplate is changing the base process architecture to 64 bits. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/8761aleabf@aptiva.optonline.net
Re: Moving from a 686-pae kernel to amd64?
Thank you I will use the 64 bit one. Thanks again. Moe On 02/28/2015 05:51 PM, Bob Proulx wrote: Linux-Fan wrote: Maureen L Thomas wrote: My new toshiba is a 64 bit amd system. It has 6G of memory and 750G hard drive. Is the 64 bit system better or should I install the 32 bit. I am using weezy. I recommend you to install the 64 bit version so that a single process is able to address more than two GiB of RAM (can be useful with data compression like 7z and other software which can make use a lot of RAM). Agreed. 6G and a pristine new system install then I would install an amd64 64-bit system. Actually even with 4G I usually install 64-bit anyway just for consistency with the new direction everything is moving. But as you can see I do still have 32-bit systems and I am not converting them to 64-bit as a conversion. Bob -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/54f2907d.9020...@tampabay.rr.com
Re: Moving from a 686-pae kernel to amd64?
Bob Proulx b...@proulx.com writes: Sharon Kimble wrote: This setup is currently running a 3.16.0-4-686-pae kernel. Is it a good idea to convert to a 64bit kernel, specifically 3.16.0-4-amd64? How much memory do you have in your system? 4G actual, 3.84g useable. If the answer is 4G or less then there is no advantage. Stay with the 32-bit kernel. If the answer is 64G or more then yes you should definitely use a 64-bit kernel. If the answer is between 4G and 64G then the answer is it depends and there are advantages and disadvantages to both. If you currently have a 32-bit system then I recommend staying there. A 64-bit kernel won't have much advantage for a 32-bit userspace. It is rather a pain to change from 32-bit userland to 64-bit. Not really worth it. Is your web browser exceeding 3G of ram image? No, but I do have 2 browsers open for a project I'm working on. If the answer is yes then you should re-install to a 64-bit userland. If the answer is no then stick with 32-bits. And if it is a good idea, how do I do it? Is it as simple as downloading the 3.16.0-4-amd64 kernel, reboot to it, and delete the 3.16.0-4-686-pae kernel? Simply install the linux-image-amd64 metapackage, let it drag in the version numbered kernel, and then reboot to it. Thanks, that's what I thought, but I wanted to check first. # uname -a Linux joseki 3.2.0-4-686-pae #1 SMP Debian 3.2.65-1+deb7u2 i686 GNU/Linux # apt-get install linux-image-amd64 Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: linux-image-3.2.0-4-amd64 Suggested packages: linux-doc-3.2 debian-kernel-handbook The following NEW packages will be installed: linux-image-3.2.0-4-amd64 linux-image-amd64 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 23.4 MB of archives. After this operation, 105 MB of additional disk space will be used. Do you want to continue [Y/n]? Bob Thanks very much, very useful. :) Sharon. -- A taste of linux = http://www.sharons.org.uk my git repo = https://bitbucket.org/boudiccas/dots TGmeds = http://www.tgmeds.org.uk Debian testing, fluxbox 1.3.6, emacs 24.4.1.0 signature.asc Description: PGP signature
