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Kernel: Generate page fault events from the kernel profiler

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Hook the kernel page fault handler and capture page fault events when
the fault has a current thread attached in TLS. We capture the eip and
ebp so we can unwind the stack and locate which pieces of code are
generating the most page faults.

Co-authored-by: Gunnar Beutner <gbeutner@serenityos.org>
This commit is contained in:
Brian Gianforcaro 2021-05-18 02:26:11 -07:00 • committed by Andreas Kling
parent 6ac1ca5a9a
commit 83fc591cea
7 changed files with 47 additions and 2 deletions
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17
Kernel/PerformanceEventBuffer.cpp
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@ -7,6 +7,7 @@
#include <AK/JsonArraySerializer.h>
#include <AK/JsonObject.h>
#include <AK/JsonObjectSerializer.h>
#include <AK/ScopeGuard.h>
#include <Kernel/Arch/x86/SmapDisabler.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/KBufferBuilder.h>
@ -63,6 +64,17 @@ KResult PerformanceEventBuffer::append_with_eip_and_ebp(ProcessID pid, ThreadID
if ((g_profiling_event_mask & type) == 0)
return EINVAL;
auto current_thread = Thread::current();
u32 enter_count = 0;
if (current_thread)
enter_count = current_thread->enter_profiler();
ScopeGuard leave_profiler([&] {
if (current_thread)
current_thread->leave_profiler();
});
if (enter_count > 0)
return EINVAL;
PerformanceEvent event;
event.type = type;
event.lost_samples = lost_samples;
@ -122,6 +134,8 @@ KResult PerformanceEventBuffer::append_with_eip_and_ebp(ProcessID pid, ThreadID
event.data.kfree.size = arg1;
event.data.kfree.ptr = arg2;
break;
case PERF_EVENT_PAGE_FAULT:
break;
default:
return EINVAL;
}
@ -210,6 +224,9 @@ bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
event_object.add("ptr", static_cast<u64>(event.data.kfree.ptr));
event_object.add("size", static_cast<u64>(event.data.kfree.size));
break;
case PERF_EVENT_PAGE_FAULT:
event_object.add("type", "page_fault");
break;
}
event_object.add("pid", event.pid);
event_object.add("tid", event.tid);