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6b2cdc4b96
We're seeing huge slowdowns on large builds on the autobuilder. A qemux86 world build was running really slowly, a primary feature was lots of rehashing going on due to an sstate change which caused a rebuild when all output should be identical. This was traced to the hundreds of thousands of calls to get_unihash() from get_taskash(). If we simplify the unitaskhashes data structure, we can bypass the function call and access the data directly. In local profile charts, this significanly sped up process_possible_migrations(), both on profiles and visually. Whilst this change doesn't aid readability, it does solve an otherwise huge performance issue. (Bitbake rev: c4b8440f730c33eaf9f818b856ae81b2f1017fec) 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.