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Kernel: Reduce the number of sent IPIs

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Only send an IPI when the target processors don't have pending messages.
This basically gets rid of TLB shootdowns from showing up in profiles.
Before they were taking maybe >10% kernel time :^D
This commit is contained in:
Bananymous
2026-05-19 23:52:38 +03:00
parent 24c37e7381
commit 376e4b4c45
2 changed files with 15 additions and 6 deletions
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19
kernel/kernel/Processor.cpp
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@@ -488,7 +488,7 @@ namespace Kernel
set_interrupt_state(state);
}
void Processor::send_smp_message(ProcessorID processor_id, const SMPMessage& message, bool send_ipi)
bool Processor::send_smp_message(ProcessorID processor_id, const SMPMessage& message, bool send_ipi)
{
auto state = get_interrupt_state();
set_interrupt_state(InterruptState::Disabled);
@@ -499,6 +499,8 @@ namespace Kernel
{
processor.lock_tlb_lock();
const bool is_first_entry = (processor.m_tlb_entry_count == 0);
const auto& tlb_msg = message.flush_tlb;
processor.m_tlb_global |= (tlb_msg.page_table == nullptr);
@@ -515,7 +517,7 @@ namespace Kernel
processor.unlock_tlb_lock();
set_interrupt_state(state);
return;
return is_first_entry;
}
// find a slot for message
@@ -557,15 +559,19 @@ namespace Kernel
storage->next = processor.m_smp_pending;
}
const bool needs_ipi = (storage->next == nullptr);
if (send_ipi)
{
if (processor_id == current_id())
handle_smp_messages();
else
else if (needs_ipi)
InterruptController::get().send_ipi(processor_id);
}
set_interrupt_state(state);
return needs_ipi;
}
void Processor::broadcast_smp_message(const SMPMessage& message)
@@ -576,15 +582,18 @@ namespace Kernel
const auto state = get_interrupt_state();
set_interrupt_state(InterruptState::Disabled);
bool needs_ipi = false;
const auto current_id = Processor::current_id();
for (size_t i = 0; i < Processor::count(); i++)
{
const auto processor_id = s_processor_ids[i];
if (processor_id != current_id)
send_smp_message(processor_id, message, false);
needs_ipi |= send_smp_message(processor_id, message, false);
}
InterruptController::get().broadcast_ipi();
if (needs_ipi)
InterruptController::get().broadcast_ipi();
set_interrupt_state(state);
}