c56004901f
This adds VM op batching to skas0. Rather than having a context switch to and from the userspace stub for each address space change, we write a number of operations to the stub data page and invoke a different stub which loops over them and executes them all in one go. The operations are stored as [ system call number, arg1, arg2, ... ] tuples. The set is terminated by a system call number of 0. Single operations, i.e. page faults, are handled in the old way, since that is slightly more efficient. For a kernel build, a minority (~1/4) of the operations are part of a set. These sets averaged ~100 in length, so for this quarter, the context switching overhead is greatly reduced. Signed-off-by: Jeff Dike <jdike@addtoit.com> Cc: Paolo Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
37 lines
665 B
ArmAsm
37 lines
665 B
ArmAsm
#include "uml-config.h"
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.globl syscall_stub
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.section .__syscall_stub, "x"
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syscall_stub:
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syscall
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/* We don't have 64-bit constants, so this constructs the address
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* we need.
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*/
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movq $(UML_CONFIG_STUB_DATA >> 32), %rbx
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salq $32, %rbx
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movq $(UML_CONFIG_STUB_DATA & 0xffffffff), %rcx
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or %rcx, %rbx
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movq %rax, (%rbx)
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int3
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.globl batch_syscall_stub
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batch_syscall_stub:
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movq $(UML_CONFIG_STUB_DATA >> 32), %rbx
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salq $32, %rbx
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movq $(UML_CONFIG_STUB_DATA & 0xffffffff), %rcx
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or %rcx, %rbx
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movq %rbx, %rsp
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again: pop %rax
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cmpq $0, %rax
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jz done
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pop %rdi
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pop %rsi
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pop %rdx
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pop %r10
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pop %r8
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pop %r9
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syscall
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mov %rax, (%rbx)
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jmp again
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done: int3
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