-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 01/02/2014 06:16 PM, Stan Hoeppner wrote: > Thank you for this information. Now, if I actually had a 4K drive > in my hands, and plugged it in, directly formatted it with XFS, no > partitions, would the LBA addressing be 4K or 512B? Or would I > need to tweak kernel parameters? Or possibly rebuild my kernel to > support 4K sectors? Addressing would be in 4k sectors, no need for tweaking. You can see it in action with the scsi_debug module if you don't have the actual hardware. > It's not relevant because you don't create an md RAID set from > CD-ROM. Well the context wasn't specifically for md; you claimed linux did not support non 512 byte sectors full stop. And you *can* build an md raid on top of cd/dvd-rw, though obviously that's a little nutty. > IIRC, there was a lengthy discussion about this on mm back when > some folks wanted to use 16K-4GB pages on Itanium, and later 2M > pages on x86-64, to cut down on the amount of memory required for > page tables and to increase performance for big memory workloads. > As I recall the arguments for continuing to use 4K pages across the > world of Linux, regardless of architecture capability, and to NOT > make it configurable as in HP-UX, were, paraphrasing: Some archs don't support 4k pages at all. > 1. The kernel manipulates "everything" in pages so we need > consistency 2. While larger pages saves page table space and > increases throughput for large memory intensive workloads, it > causes more waste in other structures and increases bandwidth > demands for data that are smaller than the page size > > So, IIRC, it was decided that the page size would remain 4K > basically forever. So while it is *technically* possible to have a > larger page size in Linux, it is absolutely not supported by the > kernel team, nor any distro kernel, AFAIK. Yep, that's why the default on those archs that have a choice is still 4k, but some do give the option for larger. If you scan the ext4 and md mailing lists you should find a few discussions of people doing this, or just using larger block sizes on archs that only support larger page sizes. > And I'd guess a whole host of things will likely break as a result > if you don't correctly modify much of the kernel source before > running make. See above. Nope; otherwise it wouldn't be a Kconfig option. Remember, the kernel had to grow support for non 4k pages to work at all on archs that don't support them. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCgAGBQJSxgwRAAoJEI5FoCIzSKrwVBIH/2XxI7Pz7pb5ojV94Xg7om2Y drEebKn5N+QFXQGXkMZFknFSDGuv4l/KgNmPbU43ntXmAi/U+HyepMtFl4K4tPVd lgSxNE7oikEMgHV5mKa4Ic0iB46AUp7cuhvyGe3FVxC+co9+J8hWgr11iYCCP2ra 9d7TT2hQEHELSvzWVoYWbh7ndV9ZfB5LC6dsRlqu0OKPlkX5xg/H7jlEgpqb0/Uc ebJ4CidYtKVMsW5My3K7uG1T4uZoB6QTNEDaYzfJjw+5KAKAR60TZXttADt670yk BPpU55UbFZTBgUyKIuYsxIZ2mgZKNTd3BT4jWOb+J5Z3+KPbN/nuHhAWqwIE+24= =6YGJ -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
