I'm trying to run my 2.6.14 Gentoo distro on a 7447A system I have with different cache configurations (ie, write back vs write thru) for both the kernel, system apps (sshd, etc) and user apps. I first wanted to run entirely in Write-Thru to get a worst-case benchmark, but after discovering (to my chagrin) that the 7447A doesn't honor the L2CR_L2WT bit, I tried something a bit more adventurous by setting the WIMG bits on the linux PTE's in the arch/ppc files.
Rather, I thought I would. Nothing I've tried seems to work. In arch/ppc/mm/ppc_mmu.c Adding _PAGE_WRITETHRU to the _PAGE_RAM flag in the setbat calls at lines 112 & 120 results in a kernel that won't go past the "Uncompressing" step. In arch/ppc/mm/pgtables.c If I add _PAGE_WRITETHRU to the _PAGE_RAM flag in mapin_ram and map_page allows the kernel to boot, and in fact shows no noticable performance difference. I found in arch/ppc/mm/hashtable.S that the linux PTE's aren't entirely transferred into the HPTE's of the PPC, so with some reluctance, I tried adding a line turning on WRITETHRU at line 350 in create_hpte: ori r8,r8,_PAGE_WRITETHRU The kernel will come up, but init promptly dies with Signal 11. There's little documentation on PPC Memory management & the linux kernel, so I'm not sure what do to from here. Can anyone help me out here? Thanks. Matt _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
