4 ms·

It didn't save the x87 FPU registers either, however a task switch set a flag in MSW / CR0 that caused a trap on the next instruction using these registers. The

It didn't save the x87 FPU registers either, however a task switch set a flag in MSW / CR0 that caused a trap on the next instruction using these registers. The idea is that they are used infrequently, so it's better to only switch the FPU context when required. This is no longer so true today, however the Linux kernel for example doesn't use any floating point or vector instructions, in order to avoid having to save these registers on every system call or interrupt. The real inflexibility was scheduling (see my other comment)

lights0123 3y ago
> the Linux kernel for example doesn't use any floating point or vector instructions it doesn't use them by default, but code that needs the FPU can call kernel_fpu_begin() to save those registers if needed. https://yarchive.net/comp/linux/kernel_fp.html https://yarchive.net/comp/linux/kernel_fp.html One big user is the AMD graphics driver: https://lore.kernel.org/amd-gfx/ee26b06b-f1a0-5a8f-388c-13c1072ae03e@amd.com/T/ https://lore.kernel.org/amd-gfx/ee26b06b-f1a0-5a8f-388c-13c1...