On 11/03/2014 13:52, David Daney wrote: > On 11/02/2014 02:53 AM, Joshua Kinard wrote: >> >> So I have been testing the Onyx2 I have out the last few days with the IOC3 >> metadriver used on Octane, and I can get it to boot, but if >> CONFIG_TRANSPARENT_HUGEPAGE is enabled in the kernel, bus errors can happen. >> >> If I use CONFIG_PAGE_SIZE_4KB, I get bus errors rather frequently -- running >> Gentoo's 'emerge' command can produce one. Switch to CONFIG_PAGE_SIZE_16KB, >> and the bus errors are far less frequent. I suspect CONFIG_PAGE_SIZE_64KB will >> be even less. >> >> Disable CONFIG_TRANSPARENT_HUGEPAGE, and the machine works pretty good. It's >> been up for almost 8 hours compiling, and not a single bus error yet. It's got >> 2x node board with dual R12K/400MHz CPUs per node. >> >> I'm not really sure what CONFIG_TRANSPARENT_HUGEPAGE is enabling that's causing >> R12K CPUs on the IP27 such a headache (and on Octane, really screws up R14K >> CPUs). I tried getting a core dump on one of the bus errors, but that >> produces a >> truncated or corrupted core file that actually crashed GDB, plus I get a nice >> oops message in dmesg: > > Well, as its name implies, if you enable CONFIG_TRANSPARENT_HUGEPAGE, huge > pages will be created and used in the background transparently to the userspace > application. > > With 4KB base page size, the huge pages will be 2MB in size.. I don't know > much about the R10K/R12K/R14K CPUs, but it is possible that either their TLBs > cannot handle such pages, or that the TLB Exception handlers don't contain > proper code for these CPUs. > > For each doubling of the base PAGE_SIZE, the huge page size will increase by a > factor of 4. So with 16KB base pages the huge page size would be 32MB, since > there are many fewer opportunities to transparently use a 32MB page, I would > expect any errors related to huge pages to be correspondingly less frequent. > > With 64KB PAGE_SIZE the huge page size is 512MB, and It is likely that that > could never be used by normal userspace programs. I checked the R10K/R12K manual, and the PageMask register there has bits 24:13 open for setting a mask value. It looks like these CPUs only support a page size from 4KB to 16MB (so a 2MB page size should work w/ transparent hugepages). I assume that the R14K on the Octane might be the same (but I don't have a manual specific to the R14k, so I don't know). All of the remaining bits in that register read 0 and must have 0's written back. I guess I could find a way to have the kernel trigger a non-fatal oops/dump the registers on a bus error and get a look at the cause register to see if that sheds any light on things. Doesn't a SIGBUS on MIPS typically mean that an address wasn't aligned on a 32-bit boundary? Or could it also mean other things? I believe that the R10K is largely compatible with the R4K-style TLB setup, but Ralf or someone else more knowledge in that area will have to verify. Maybe the R10k-family CPUs need their own TLB routines, or what currently exists needs modifications? I have not tried to understand the whole TLB thing in MIPS yet, so that's a bit of voodoo to me. --J >> [ 1302.260000] CPU: 0 PID: 1179 Comm: emerge Not tainted >> 3.17.1-mipsgit-20141006 #57 >> [ 1302.260000] task: a8000000ffbbf288 ti: a8000000fa6f0000 task.ti: >> a8000000fa6f0000 >> [ 1302.260000] $ 0 : 0000000000000000 0000000000000001 0000000000000000 >> a8000000ff5ad800 >> [ 1302.260000] $ 4 : a8000000006d5480 00000000000f9c00 00000001f380173f >> a800000001000000 >> [ 1302.260000] $ 8 : 00000001f380173f 0000000000100077 a8000000fe77a000 >> 0000000000000000 >> [ 1302.260000] $12 : 0000000000660000 0000000000000000 0000000000000000 >> 776bc40c00000004 >> [ 1302.260000] $16 : 0000000000e00000 0000000000000000 00000000018ee000 >> 6db6db6db6db6db7 >> [ 1302.260000] $20 : 00000000000000ca a8000000006d5480 a8000000ff65fa68 >> 0000000000001000 >> [ 1302.260000] $24 : 0000000000000000 a8000000000469c0 >> [ 1302.260000] $28 : a8000000fa6f0000 a8000000fa6f3a00 0000000000e00000 >> a800000000046720 >> [ 1302.260000] Hi : 00000000002ed400 >> [ 1302.260000] Lo : 00000000000f9c00 >> [ 1302.260000] epc : a8000000000467e4 r4k_flush_cache_page+0x104/0x2e0 >> [ 1302.260000] Not tainted >> [ 1302.260000] ra : a800000000046720 r4k_flush_cache_page+0x40/0x2e0 >> [ 1302.260000] Status: 90001ce3 KX SX UX KERNEL EXL IE >> [ 1302.260000] Cause : 0000c010 >> [ 1302.260000] BadVA : 00000001f380173f >> [ 1302.260000] PrId : 00000e35 (R12000) >> [ 1302.260000] Process emerge (pid: 1179, threadinfo=a8000000fa6f0000, >> task=a8000000ffbbf288, tls=00000000778d2490) >> [ 1302.260000] Stack : a8000000ff65fa68 0000000000e00000 00000000000f9c00 >> a8000000006d5480 >> a8000000ff65fa68 0000000000001000 0000000000e00000 a80000000010cb00 >> a8000000046a2000 a8000000ff65fa68 00000000018ee000 6db6db6db6db6db7 >> a8000000fe7fdce0 a8000000000375ec a8000000ff4e5800 a8000000005fbd90 >> 0000000300000080 a8000000ff668580 a8000000005fbd90 5349474900000080 >> a8000000fa6f3ad8 a8000000005fbd90 0000000600000088 a8000000ff5ad928 >> a8000000005fbd90 46494c4500002bf9 c000000000101000 0000000a00000080 >> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >> ... >> [ 1302.260000] Call Trace: >> [ 1302.260000] [<a8000000000467e4>] r4k_flush_cache_page+0x104/0x2e0 >> [ 1302.260000] [<a80000000010cb00>] get_dump_page+0xc8/0xe8 >> [ 1302.260000] [<a8000000000375ec>] elf_core_dump+0x1294/0x14d8 >> [ 1302.260000] [<a8000000001b41e4>] do_coredump+0x5e4/0x1048 >> [ 1302.260000] [<a80000000005c0b8>] get_signal+0x1b8/0x710 >> [ 1302.260000] [<a8000000000299c0>] do_signal+0x18/0x240 >> [ 1302.260000] [<a80000000002a4c8>] do_notify_resume+0x70/0x88 >> [ 1302.260000] [<a8000000000255ac>] work_notifysig+0x10/0x18 >> [ 1302.260000] >> [ 1302.260000] >> Code: 0010327a 30c60ff8 00c8302d <dcc60000> 30c80001 1100003e 00000000 >> bfb40000 df880000 >> [ 1305.340000] ---[ end trace c7649a6433db8d18 ]--- >> >> Thoughts? -- Joshua Kinard Gentoo/MIPS kumba@xxxxxxxxxx 4096R/D25D95E3 2011-03-28 "The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between." --Emperor Turhan, Centauri Republic
