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In Yocto Project PR 13992 it was reported that qemumips in autobuilder runs almost twice slower then qemumips64 and some times hit time out. Upon investigations of qemu-system with perf, gdb, and SystemTap and comparing qemumips and qemumips64 machines behavior it was noticed that qemu soft mmu code behaves quite different and in case if qemumips tlbwr instruction called 16 times more oftern. It happens that in qemumips64 case qemu runs with cpu type that contains 64 TLB, but in case of qemumips qemu runs with cpu type that contains only 16 TLBs. The idea of proposed qemu patch is to introduce fictitious 34Kf-64tlb cpu type that defined exactly as 34Kf but has 64 TLBs, instead of original 16 TLBs. Testing of core-image-full-cmdline:do_testimage with 34Kf-64tlb shows 40% or so test execution real time improvement. Note for future porters of the patch: easiest way to update the patch and be in sync with 34Kf definition is to copy 34Kf machine definition and apply the following changes to it (just change 15 to 63 of CP0C1_MMU bits value) [kamensky@coreos-lnx2 qemu]$ diff ~/34Kf.c ~/34Kf-64tlb.c 2c2 < .name = "34Kf", > .name = "34Kf-64tlb", 6c6 < .CP0_Config1 = MIPS_CONFIG1 | (1 << CP0C1_FP) | (15 << CP0C1_MMU) | > .CP0_Config1 = MIPS_CONFIG1 | (1 << CP0C1_FP) | (63 << CP0C1_MMU) | Fixes https://bugzilla.yoctoproject.org/show_bug.cgi?id=13992 Upstream Status: Inappropriate (From OE-Core rev: 4470a04943352224955f17e004962f0f9e1c9b0c) Signed-off-by: Victor Kamensky <kamensky@cisco.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
QEMU Emulation Targets ====================== To simplify development, the build system supports building images to work with the QEMU emulator in system emulation mode. Several architectures are currently supported in 32 and 64 bit variants: * ARM (qemuarm + qemuarm64) * x86 (qemux86 + qemux86-64) * PowerPC (qemuppc only) * MIPS (qemumips + qemumips64) Use of the QEMU images is covered in the Yocto Project Reference Manual. The appropriate MACHINE variable value corresponding to the target is given in brackets.