runtime: implement cheaper context switch on Linux/AMD64
Currently, goroutine switches are implemented with libc
getcontext/setcontext functions, which saves/restores the machine
register states and also the signal context. This does more than
what we need, and performs an expensive syscall.
This CL implements a simplified version of getcontext/setcontext,
in assembly, that only saves/restores the necessary part, i.e.
the callee-save registers, and the PC, SP. A simplified version
of makecontext, written in C, is also added. Currently this is
only implemented on Linux/AMD64.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/178298
From-SVN: r271818
2019-05-31 19:56:36 +02:00
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// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This provides a simplified version of getcontext and
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// setcontext. They are like the corresponding functions
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// in libc, but we only save/restore the callee-save
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// registers and PC, SP. Unlike the libc functions, we
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// don't save/restore the signal masks and floating point
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// environment.
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#if defined(__x86_64__) && defined(__linux__) && !defined(__CET__)
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#define RBP_OFF (0*8)
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#define RBX_OFF (1*8)
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#define R12_OFF (2*8)
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#define R13_OFF (3*8)
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#define R14_OFF (4*8)
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#define R15_OFF (5*8)
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#define SP_OFF (6*8)
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#define PC_OFF (7*8)
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.globl __go_getcontext
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.text
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__go_getcontext:
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movq %rbx, RBX_OFF(%rdi)
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movq %rbp, RBP_OFF(%rdi)
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movq %r12, R12_OFF(%rdi)
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movq %r13, R13_OFF(%rdi)
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movq %r14, R14_OFF(%rdi)
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movq %r15, R15_OFF(%rdi)
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movq (%rsp), %rax // return PC
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movq %rax, PC_OFF(%rdi)
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leaq 8(%rsp), %rax // the SP before pushing return PC
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movq %rax, SP_OFF(%rdi)
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ret
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.globl __go_setcontext
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.text
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__go_setcontext:
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movq RBX_OFF(%rdi), %rbx
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movq RBP_OFF(%rdi), %rbp
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movq R12_OFF(%rdi), %r12
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movq R13_OFF(%rdi), %r13
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movq R14_OFF(%rdi), %r14
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movq R15_OFF(%rdi), %r15
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movq SP_OFF(%rdi), %rsp
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movq PC_OFF(%rdi), %rdx
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jmp *%rdx
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.globl __go_makecontext
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.text
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__go_makecontext:
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addq %rcx, %rdx
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// Align the SP, and push a dummy return address.
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2019-06-03 22:06:50 +02:00
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andq $~0xf, %rdx
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runtime: implement cheaper context switch on Linux/AMD64
Currently, goroutine switches are implemented with libc
getcontext/setcontext functions, which saves/restores the machine
register states and also the signal context. This does more than
what we need, and performs an expensive syscall.
This CL implements a simplified version of getcontext/setcontext,
in assembly, that only saves/restores the necessary part, i.e.
the callee-save registers, and the PC, SP. A simplified version
of makecontext, written in C, is also added. Currently this is
only implemented on Linux/AMD64.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/178298
From-SVN: r271818
2019-05-31 19:56:36 +02:00
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subq $8, %rdx
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movq $0, (%rdx)
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movq %rdx, SP_OFF(%rdi)
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movq %rsi, PC_OFF(%rdi)
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ret
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2019-10-02 22:11:35 +02:00
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.section .note.GNU-split-stack,"",@progbits
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.section .note.GNU-no-split-stack,"",@progbits
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runtime: implement cheaper context switch on Linux/AMD64
Currently, goroutine switches are implemented with libc
getcontext/setcontext functions, which saves/restores the machine
register states and also the signal context. This does more than
what we need, and performs an expensive syscall.
This CL implements a simplified version of getcontext/setcontext,
in assembly, that only saves/restores the necessary part, i.e.
the callee-save registers, and the PC, SP. A simplified version
of makecontext, written in C, is also added. Currently this is
only implemented on Linux/AMD64.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/178298
From-SVN: r271818
2019-05-31 19:56:36 +02:00
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#endif
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2019-12-05 18:51:10 +01:00
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.section .note.GNU-stack,"",@progbits
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