Re: Why is AHCI built-in?
On 08/28/2013 12:46 AM, poma wrote: On 19.08.2013 20:46, Kyle McMartin wrote: On Mon, Aug 19, 2013 at 01:35:16PM -0500, Ian Pilcher wrote: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? performance, you'll take fewer tlb misses. Any links/docs to offer on this topic? http://tldp.org/HOWTO/Module-HOWTO/x627.html#MEMALLOC -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On Wed, Aug 28, 2013 at 12:46:31AM +0200, poma wrote: Any links/docs to offer on this topic? Thanks. I don't have a link off-hand, but a book about computer architecture should let you figure things out: At what level of detail? The kernel attempts to map itself using 2MB pages on X86 where possible (since it's large and contiguous.) For various reasons, modules are mapped using 4K pages since they'd need to be padded out to 2MB (very little module .text would be that big, and obviously code and data are mapped separately for protection reasons.) Also, separate modules need to be on separate pages in order to ensure that you can remove them independently. So the more modules you have loaded, the more likely useful TLB (translation lookaside buffer, which caches virtual to physical mappings) from userspace will get pushed out by the kernel on a system call or interrupt. regards, Kyle -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 28.08.2013 16:57, Kyle McMartin wrote: On Wed, Aug 28, 2013 at 12:46:31AM +0200, poma wrote: Any links/docs to offer on this topic? Thanks. I don't have a link off-hand, but a book about computer architecture should let you figure things out: At what level of detail? The kernel attempts to map itself using 2MB pages on X86 where possible (since it's large and contiguous.) For various reasons, modules are mapped using 4K pages since they'd need to be padded out to 2MB (very little module .text would be that big, and obviously code and data are mapped separately for protection reasons.) Also, separate modules need to be on separate pages in order to ensure that you can remove them independently. So the more modules you have loaded, the more likely useful TLB (translation lookaside buffer, which caches virtual to physical mappings) from userspace will get pushed out by the kernel on a system call or interrupt. regards, Kyle This is a good starting point. Thank you. poma -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 28.08.2013 15:14, Michal Schmidt wrote: On 08/28/2013 12:46 AM, poma wrote: On 19.08.2013 20:46, Kyle McMartin wrote: On Mon, Aug 19, 2013 at 01:35:16PM -0500, Ian Pilcher wrote: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? performance, you'll take fewer tlb misses. Any links/docs to offer on this topic? http://tldp.org/HOWTO/Module-HOWTO/x627.html#MEMALLOC Thank you for reminding me on this one. :) poma -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 19.08.2013 20:46, Kyle McMartin wrote: On Mon, Aug 19, 2013 at 01:35:16PM -0500, Ian Pilcher wrote: On 08/19/2013 01:19 PM, Kyle McMartin wrote: because it's commonly used and found on basically every machine now. there are many advantages to having it built in that outweigh the cons. A couple of questions: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? performance, you'll take fewer tlb misses. Any links/docs to offer on this topic? Thanks. poma -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On Mon, 19 Aug 2013 13:16:03 -0500 Ian Pilcher arequip...@gmail.com wrote: (I want to rebuild it with LED triggers for the disk LEDs on my NAS.) Frankly this sounds like madness. You need to build a kernel, it's trivial -- just edit one of configs and rpmbuild -ba, and then you have very clear delineation of what upgrades what and what depends on what. -- Pete -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Why is AHCI built-in?
Somewhere along the line, the AHCI driver was changed from a module to being built-in to the kernel. This is a major PITA for anyone who wants to use a different/customized version of this driver. (I want to rebuild it with LED triggers for the disk LEDs on my NAS.) I haven't been able to find anything in git or BZ about why this was done, probably because searching on ahci and module in Bugzilla isn't exactly productive. Any pointers? TIA -- Ian Pilcher arequip...@gmail.com Sometimes there's nothing left to do but crash and burn...or die trying. -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On Mon, Aug 19, 2013 at 01:16:03PM -0500, Ian Pilcher wrote: Somewhere along the line, the AHCI driver was changed from a module to being built-in to the kernel. This is a major PITA for anyone who wants to use a different/customized version of this driver. (I want to rebuild it with LED triggers for the disk LEDs on my NAS.) I haven't been able to find anything in git or BZ about why this was done, probably because searching on ahci and module in Bugzilla isn't exactly productive. because it's commonly used and found on basically every machine now. there are many advantages to having it built in that outweigh the cons. --kyle -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 08/19/2013 01:19 PM, Kyle McMartin wrote: because it's commonly used and found on basically every machine now. there are many advantages to having it built in that outweigh the cons. A couple of questions: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? - Was this change discussed anywhere? Thanks! -- Ian Pilcher arequip...@gmail.com Sometimes there's nothing left to do but crash and burn...or die trying. -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On Mon, Aug 19, 2013 at 01:35:16PM -0500, Ian Pilcher wrote: On 08/19/2013 01:19 PM, Kyle McMartin wrote: because it's commonly used and found on basically every machine now. there are many advantages to having it built in that outweigh the cons. A couple of questions: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? performance, you'll take fewer tlb misses. - Was this change discussed anywhere? among the fedora kernel team at plumbers conf in 2008. --kyle -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 19 Aug 2013 19:40, Ian Pilcher arequip...@gmail.com wrote: On 08/19/2013 01:19 PM, Kyle McMartin wrote: because it's commonly used and found on basically every machine now. there are many advantages to having it built in that outweigh the cons. A couple of questions: - What are the advantages of having the driver built-in, as compared to simply ensuring that it's always included in the initramfs? Easy support for the most commonly used options, things like the IP and the Intel sata driver are built in as well for similar means. Ultimately if there's missing features you should communicate with the author of the patch as to why they're not upstream and then you'd not have to care about whether its built in or a module. - Was this change discussed anywhere? Probably on the kernel list if anywhere, I vaguely remember reading about it. Peter -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
Re: Why is AHCI built-in?
On 08/19/2013 01:48 PM, Peter Robinson wrote: Ultimately if there's missing features you should communicate with the author of the patch as to why they're not upstream and then you'd not have to care about whether its built in or a module. Heh. I kind of doubt that the AHCI driver maintainers are interested in adding hardware-specific LED triggers. Probably on the kernel list if anywhere, I vaguely remember reading about it. Pointed to the discussion (back in 2008!) by a co-worker. I didn't even know that Fedora had its own kernel list. (I wrongly assumed that this change post-dated the RHEL 6 branch, since AHCI is still a module in RHEL 6.) Thanks for the info! -- Ian Pilcher arequip...@gmail.com Sometimes there's nothing left to do but crash and burn...or die trying. -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
