gotosocial/vendor/github.com/cilium/ebpf/asm/jump.go
Daniele Sluijters acc333c40b
[feature] Inherit resource limits from cgroups (#1336)
When GTS is running in a container runtime which has configured CPU or
memory limits or under an init system that uses cgroups to impose CPU
and memory limits the values the Go runtime sees for GOMAXPROCS and
GOMEMLIMIT are still based on the host resources, not the cgroup.

At least for the throttling middlewares which use GOMAXPROCS to
configure their queue size, this can result in GTS running with values
too big compared to the resources that will actuall be available to it.

This introduces 2 dependencies which can pick up resource contraints
from the current cgroup and tune the Go runtime accordingly. This should
result in the different queues being appropriately sized and in general
more predictable performance. These dependencies are a no-op on
non-Linux systems or if running in a cgroup that doesn't set a limit on
CPU or memory.

The automatic tuning of GOMEMLIMIT can be disabled by either explicitly
setting GOMEMLIMIT yourself or by setting AUTOMEMLIMIT=off. The
automatic tuning of GOMAXPROCS can similarly be counteracted by setting
GOMAXPROCS yourself.
2023-01-17 20:59:04 +00:00

109 lines
2.7 KiB
Go

package asm
//go:generate stringer -output jump_string.go -type=JumpOp
// JumpOp affect control flow.
//
// msb lsb
// +----+-+---+
// |OP |s|cls|
// +----+-+---+
type JumpOp uint8
const jumpMask OpCode = aluMask
const (
// InvalidJumpOp is returned by getters when invoked
// on non branch OpCodes
InvalidJumpOp JumpOp = 0xff
// Ja jumps by offset unconditionally
Ja JumpOp = 0x00
// JEq jumps by offset if r == imm
JEq JumpOp = 0x10
// JGT jumps by offset if r > imm
JGT JumpOp = 0x20
// JGE jumps by offset if r >= imm
JGE JumpOp = 0x30
// JSet jumps by offset if r & imm
JSet JumpOp = 0x40
// JNE jumps by offset if r != imm
JNE JumpOp = 0x50
// JSGT jumps by offset if signed r > signed imm
JSGT JumpOp = 0x60
// JSGE jumps by offset if signed r >= signed imm
JSGE JumpOp = 0x70
// Call builtin or user defined function from imm
Call JumpOp = 0x80
// Exit ends execution, with value in r0
Exit JumpOp = 0x90
// JLT jumps by offset if r < imm
JLT JumpOp = 0xa0
// JLE jumps by offset if r <= imm
JLE JumpOp = 0xb0
// JSLT jumps by offset if signed r < signed imm
JSLT JumpOp = 0xc0
// JSLE jumps by offset if signed r <= signed imm
JSLE JumpOp = 0xd0
)
// Return emits an exit instruction.
//
// Requires a return value in R0.
func Return() Instruction {
return Instruction{
OpCode: OpCode(JumpClass).SetJumpOp(Exit),
}
}
// Op returns the OpCode for a given jump source.
func (op JumpOp) Op(source Source) OpCode {
return OpCode(JumpClass).SetJumpOp(op).SetSource(source)
}
// Imm compares dst to value, and adjusts PC by offset if the condition is fulfilled.
func (op JumpOp) Imm(dst Register, value int32, label string) Instruction {
if op == Exit || op == Call || op == Ja {
return Instruction{OpCode: InvalidOpCode}
}
return Instruction{
OpCode: OpCode(JumpClass).SetJumpOp(op).SetSource(ImmSource),
Dst: dst,
Offset: -1,
Constant: int64(value),
Reference: label,
}
}
// Reg compares dst to src, and adjusts PC by offset if the condition is fulfilled.
func (op JumpOp) Reg(dst, src Register, label string) Instruction {
if op == Exit || op == Call || op == Ja {
return Instruction{OpCode: InvalidOpCode}
}
return Instruction{
OpCode: OpCode(JumpClass).SetJumpOp(op).SetSource(RegSource),
Dst: dst,
Src: src,
Offset: -1,
Reference: label,
}
}
// Label adjusts PC to the address of the label.
func (op JumpOp) Label(label string) Instruction {
if op == Call {
return Instruction{
OpCode: OpCode(JumpClass).SetJumpOp(Call),
Src: PseudoCall,
Constant: -1,
Reference: label,
}
}
return Instruction{
OpCode: OpCode(JumpClass).SetJumpOp(op),
Offset: -1,
Reference: label,
}
}