Fixes#2443
I found out with some profiling that this we were spending a decent
amount of time with the `openat` syscall in heavily utilized situations.
While not super common in active gameplay situations, it matters
significantly in loading screens that this is fairly optimal.
The bulk of the time is spent in the emulated files handler to ensure
that whatever path we are given, we can capture file paths that we need
to emulate. The largest contributor being the std::filesystem::canonical
function call.
A couple of optimizations in place here.
1) Do a quick hashmap check right at the start to see if we exactly fit
2) Change from `std::fs::canonical` to `realpath`
3) Switch `GetEmulatedFDPath` to not use optional so it stops building
on the stack
I'm still not super happy with the performance of `realpath` and also
not happy that we still need to use `lexically_normal` in one code path.
But short of writing a super hand-optimized `realpath` that fits our
constraints, I don't think we can do better.
Micro benchmark needs to test four different situations due to this
optimization.
1) Non-EmuFD path
2) Non-EmuFD path with dirfs
3) EmuFD path
4) EmuFD path with dirfs
And the performance improvement for each situation respectively
1) 12% performance improvement
- 213413 openat syscalls/s -> 238999 syscalls/s
2) 17% performance improvement
- 202085 openat syscalls/s -> 237309 syscalls/s
3) 17% performance improvement (/proc/cpuinfo)
- 56616 openat syscalls/s -> 66231 syscalls/s
- Includes overhead of generating temp FD and close syscall
4) 5% performance improvement (/proc/cpuinfo)
- 51080 openat syscalls/s -> 53956 syscalls/s
- Includes overhead of generating temp FD and close syscall
And for sake of comparison to the non-emulated system; My test system
can hit around 1-1.1 million openat syscalls per second in the same
microbench.
Nice little performance uplift.
This has been a long time coming. The C interface has been a thorn in
our side for no reason for a long time.
The purpose of this step is to remove the C interface without changing
behaviour as much as possible. This means that with this commit there
are still some bad practices but the remaining issues will be solved
with followup PRs.
Primarily, we still have a `DestroyContext(CTX)` static function which calls
the Context implementation's `DestroyContext` and does a raw C++ delete.
Follow up PR will remove that, but I didn't want to touch it yet since
it'll require checking to ensure the unique_ptr changes play nice with
our allocator hooking. Which this is already a huge PR without trying to
change behaviour.
`GetEmulatedPath` and `OpenAt` are called a /lot/ in applications.
std::filesystem::path handling here is quite heavy and costly for what
we are trying to achieve.
Remove this usage and instead use lstat, access, and readlink directly
which is a heck of a lot faster.
In particular this helps out pressure-vessel, shaving off launch times
by 1-2 seconds.
Going from ~22 seconds down to ~20 seconds.
std::filesystem::canonical is very heavyweight and walks the full path
to ensure that each folder in the path is not a symlink.
eg:
```
readlink("/proc", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/self", "880556", 1023) = 6
readlink("/proc/880556", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/880556/fd", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/proc/880556/fd/5", "/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-6"..., 1023) = 86
readlink("/home", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
readlink("/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2", 0x7ffd5646e210, 1023) = -1 EINVAL (Invalid argument)
```
This is what was occuring for every single mmap that occurs. /really/
adding to the time for the syscall to take.
This also happens on a couple of other syscalls which are using this new
path now.
The primary reason why this works is that we know that every entry in
`/proc/self/fd/` is a symlink. So instead of asking for canonical, we
can just read the symlink and this will redirect us to the canonical
path.
So this previous example goes from 14 syscalls down to 1.
eg:
```
readlinkat(AT_FDCWD, "/proc/self/fd/5", "/home/ryanh/.fex-emu/RootFS/Ubuntu_22_04/usr/lib/x86_64-linux-gnu/ld-linux-x86-6"..., 4096) = 86
```
While this is only a minor improvement in the "typical" operating environment,
this significantly improves performance of FEX under proot or if the
rootfs lives on a network share.
Adds a header only include utility folder that can be included from
everywhere.
Contains syscall helpers for older glibc and defines for older Linux
uapi headers missing some defines.
Had some idle time so I implemented this logic.
We do some tricky logic to have a big.little configuration even with
unknown CPU core types. Promoting or demoting a single MIDR depending on
if we have a mixed configuration or not.
In a non-hybrid design we only claim product names inside the CPUID
product string.
This will appear if you `/proc/cpuinfo` or read the CPUID registers
directly
eg on Snapdragon 888:
processor : 0
model name : FEX-2112-1-g13b14b85 Cortex-A55
processor : 1
model name : FEX-2112-1-g13b14b85 Cortex-A55
processor : 2
model name : FEX-2112-1-g13b14b85 Cortex-A55
processor : 3
model name : FEX-2112-1-g13b14b85 Cortex-A55
processor : 4
model name : FEX-2112-1-g13b14b85 Cortex-A78
processor : 5
model name : FEX-2112-1-g13b14b85 Cortex-A78
processor : 6
model name : FEX-2112-1-g13b14b85 Cortex-A78
processor : 7
model name : FEX-2112-1-g13b14b85 Cortex-X1
eg on Macbook Pro VM which can't see the CPU type:
processor : 0
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 1
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 2
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 3
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 4
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 5
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 6
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
processor : 7
model name : FEX-2112-1-g13b14b85 Unknown ARM CPU
Migrates lingering instances of the old logger over to fmt where
applicable. This allows removing some of the old defines and functions.
The only remaining usages of the printf-based variant of the logger is
in Tests/LinuxSyscalls/Syscalls.cpp for the strace handling.
This isn't quite a 100% clean sweep of IWYU.
There are some false positives where clang fails.
Additionally there are still a few missed in the frontend side of things
that I didn't get to
If a 32-bit application leaves a temporary file dangling from one of the EmulatedFiles
then glibc tries to clean up the FILE object on shutdown.
This results in a crash on 32-bit applications because our memory allocator will have already cleaned up
at that point
Use raw FDs in this instance which matches better with the syscall hooking expecting raw FDs anyway.
The flags calculation is fairly intensive and we were doing it for every core.
Do it once then duplicate it per core instead
Improves generation time quite significantly. A couple of milliseconds converted to half a millisecond
Slight improvement to startup time
This was being checked by an application for kernel version. Which was
seeing too new of a kernel and using things that were unsupported.
Also removes the EmulatedMap which is an unnecessary lookup.
Sadly these things can't be split without breaking functionality so it
turns in to a bit of a mess.
SyscallHandler is very much something that is a Linux only construct and
shouldn't be in FEXCore itself. Lets the frontend register a
Syscallhandler with FEXCore. FEXCore itself is then aware of the current
syscall ABI and handles the ABI in an optimal fashion.
So it is not a 100% clean break otherwise we would lose performance.
The SignalDelegator then needs to move to the frontend since the
SyscallHandler requires it for signal based syscalls.
The CPU backend signal handling still needs to happen in FEXCore because
it is a very tight coupling with the CPU backend.
Once we need to support more Signal handling we can give the backends
cleaner support to select which specific OS handler to handle.
Ryan Houdek