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2024-01-08system/cpus: rename qemu_mutex_lock_iothread() to bql_lock()Stefan Hajnoczi1-3/+3
The Big QEMU Lock (BQL) has many names and they are confusing. The actual QemuMutex variable is called qemu_global_mutex but it's commonly referred to as the BQL in discussions and some code comments. The locking APIs, however, are called qemu_mutex_lock_iothread() and qemu_mutex_unlock_iothread(). The "iothread" name is historic and comes from when the main thread was split into into KVM vcpu threads and the "iothread" (now called the main loop thread). I have contributed to the confusion myself by introducing a separate --object iothread, a separate concept unrelated to the BQL. The "iothread" name is no longer appropriate for the BQL. Rename the locking APIs to: - void bql_lock(void) - void bql_unlock(void) - bool bql_locked(void) There are more APIs with "iothread" in their names. Subsequent patches will rename them. There are also comments and documentation that will be updated in later patches. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paul Durrant <paul@xen.org> Acked-by: Fabiano Rosas <farosas@suse.de> Acked-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Cédric Le Goater <clg@kaod.org> Acked-by: Peter Xu <peterx@redhat.com> Acked-by: Eric Farman <farman@linux.ibm.com> Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com> Acked-by: Hyman Huang <yong.huang@smartx.com> Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com> Message-id: 20240102153529.486531-2-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2023-06-01accel/tcg: include cs_base in our hash calculationsAlex Bennée1-1/+1
We weren't using cs_base in the hash calculations before. Since the arm front end moved a chunk of flags in a378206a20 (target/arm: Move mode specific TB flags to tb->cs_base) they comprise of an important part of the execution state. Widen the tb_hash_func to include cs_base and expand to qemu_xxhash8() to accommodate it. My initial benchmark shows very little difference in the runtime. Before: armhf ➜ hyperfine -w 2 -m 20 "./arm-softmmu/qemu-system-arm -cpu cortex-a15 -machine type=virt,highmem=off -display none -m 2048 -serial mon:stdio -netdev user,id=unet,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=unet -device virtio-scsi-pci -blockdev driver=raw,node-name=hd,discard=unmap,file.driver=host_device,file.filename=/dev/zen-disk/debian-bullseye-armhf -device scsi-hd,drive=hd -smp 4 -kernel /home/alex/lsrc/linux.git/builds/arm/arch/arm/boot/zImage -append 'console=ttyAMA0 root=/dev/sda2 systemd.unit=benchmark.service' -snapshot" Benchmark 1: ./arm-softmmu/qemu-system-arm -cpu cortex-a15 -machine type=virt,highmem=off -display none -m 2048 -serial mon:stdio -netdev user,id=unet,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=unet -device virtio-scsi-pci -blockdev driver=raw,node-name=hd,discard=unmap,file.driver=host_device,file.filename=/dev/zen-disk/debian-bullseye-armhf -device scsi-hd,drive=hd -smp 4 -kernel /home/alex/lsrc/linux.git/builds/arm/arch/arm/boot/zImage -append 'console=ttyAMA0 root=/dev/sda2 systemd.unit=benchmark.service' -snapshot Time (mean ± σ): 24.627 s ± 2.708 s [User: 34.309 s, System: 1.797 s] Range (min … max): 22.345 s … 29.864 s 20 runs arm64 ➜ hyperfine -w 2 -n 20 "./qemu-system-aarch64 -cpu max,pauth-impdef=on -machine type=virt,virtualization=on,gic-version=3 -display none -serial mon:stdio -netdev user,id=unet,hostfwd=tcp::2222-:22,hostfwd=tcp::1234-:1234 -device virtio-net-pci,netdev=unet -device virtio-scsi-pci -blockdev driver=raw,node-name=hd,discard=unmap,file.driver=host_device,file.filename=/dev/zen-disk/debian-bullseye-arm64 -device scsi-hd,drive=hd -smp 4 -kernel ~/lsrc/linux.git/builds/arm64/arch/arm64/boot/Image.gz -append 'console=ttyAMA0 root=/dev/sda2 systemd.unit=benchmark-pigz.service' -snapshot" Benchmark 1: 20 Time (mean ± σ): 62.559 s ± 2.917 s [User: 189.115 s, System: 4.089 s] Range (min … max): 59.997 s … 70.153 s 10 runs After: armhf Benchmark 1: ./arm-softmmu/qemu-system-arm -cpu cortex-a15 -machine type=virt,highmem=off -display none -m 2048 -serial mon:stdio -netdev user,id=unet,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=unet -device virtio-scsi-pci -blockdev driver=raw,node-name=hd,discard=unmap,file.driver=host_device,file.filename=/dev/zen-disk/debian-bullseye-armhf -device scsi-hd,drive=hd -smp 4 -kernel /home/alex/lsrc/linux.git/builds/arm/arch/arm/boot/zImage -append 'console=ttyAMA0 root=/dev/sda2 systemd.unit=benchmark.service' -snapshot Time (mean ± σ): 24.223 s ± 2.151 s [User: 34.284 s, System: 1.906 s] Range (min … max): 22.000 s … 28.476 s 20 runs arm64 hyperfine -w 2 -n 20 "./qemu-system-aarch64 -cpu max,pauth-impdef=on -machine type=virt,virtualization=on,gic-version=3 -display none -serial mon:stdio -netdev user,id=unet,hostfwd=tcp::2222-:22,hostfwd=tcp::1234-:1234 -device virtio-net-pci,netdev=unet -device virtio-scsi-pci -blockdev driver=raw,node-name=hd,discard=unmap,file.driver=host_device,file.filename=/dev/zen-disk/debian-bullseye-arm64 -device scsi-hd,drive=hd -smp 4 -kernel ~/lsrc/linux.git/builds/arm64/arch/arm64/boot/Image.gz -append 'console=ttyAMA0 root=/dev/sda2 systemd.unit=benchmark-pigz.service' -snapshot" Benchmark 1: 20 Time (mean ± σ): 62.769 s ± 1.978 s [User: 188.431 s, System: 5.269 s] Range (min … max): 60.285 s … 66.868 s 10 runs Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-id: 20230526165401.574474-12-alex.bennee@linaro.org Message-Id: <20230524133952.3971948-11-alex.bennee@linaro.org> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2021-07-21qemu/atomic: Add aligned_{int64,uint64}_t typesRichard Henderson1-2/+2
Use it to avoid some clang-12 -Watomic-alignment errors, forcing some structures to be aligned and as a pointer when we have ensured that the address is aligned. Tested-by: Cole Robinson <crobinso@redhat.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2020-09-23qemu/atomic.h: rename atomic_ to qatomic_Stefan Hajnoczi1-25/+25
clang's C11 atomic_fetch_*() functions only take a C11 atomic type pointer argument. QEMU uses direct types (int, etc) and this causes a compiler error when a QEMU code calls these functions in a source file that also included <stdatomic.h> via a system header file: $ CC=clang CXX=clang++ ./configure ... && make ../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid) Avoid using atomic_*() names in QEMU's atomic.h since that namespace is used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h and <stdatomic.h> can co-exist. I checked /usr/include on my machine and searched GitHub for existing "qatomic_" users but there seem to be none. This patch was generated using: $ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \ sort -u >/tmp/changed_identifiers $ for identifier in $(</tmp/changed_identifiers); do sed -i "s%\<$identifier\>%q$identifier%g" \ $(git grep -I -l "\<$identifier\>") done I manually fixed line-wrap issues and misaligned rST tables. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
2019-12-17qsp: Use WITH_RCU_READ_LOCK_GUARDDr. David Alan Gilbert1-12/+10
The automatic rcu read lock maintenance works quite nicely in this case where it previously relied on a comment to delimit the lifetime and now has a block. Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-09-16qemu-thread: Add qemu_cond_timedwaitYury Kotov1-0/+20
The new function is needed to implement conditional sleep for CPU throttling. It's possible to reuse qemu_sem_timedwait, but it's more difficult than just add qemu_cond_timedwait. Also moved compute_abs_deadline function up the code to reuse it in qemu_cond_timedwait_impl win32. Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru> Message-Id: <20190909131335.16848-2-yury-kotov@yandex-team.ru> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-04-18qsp: Simplify how qsp_report() printsMarkus Armbruster1-10/+11
qsp_report() takes an fprintf()-like callback and a FILE * to pass to it. Its only caller hmp_sync_profile() passes monitor_fprintf() and the current monitor cast to FILE *. monitor_fprintf() casts it right back, and is otherwise identical to monitor_printf(). The type-punning is ugly. Drop the callback, and call qemu_printf() instead. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Message-Id: <20190417191805.28198-7-armbru@redhat.com>
2018-12-17include: move exec/tb-hash-xx.h to qemu/xxhash.hEmilio G. Cota1-1/+1
Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-12-17exec: introduce qemu_xxhash{2,4,5,6,7}Emilio G. Cota1-6/+6
Before moving them all to include/qemu/xxhash.h. Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-10-02qsp: use atomic64 accessorsEmilio G. Cota1-41/+8
With the seqlock, we either have to use atomics to remain within defined behaviour (and note that 64-bit atomics aren't always guaranteed to compile, irrespective of __nocheck), or drop the atomics and be in undefined behaviour territory. Fix it by dropping the seqlock and using atomic64 accessors. This will limit scalability when !CONFIG_ATOMIC64, but those machines (1) don't have many users and (2) are unlikely to have many cores. - With CONFIG_ATOMIC64: $ tests/atomic_add-bench -n 1 -m -p Throughput: 13.00 Mops/s - Forcing !CONFIG_ATOMIC64: $ tests/atomic_add-bench -n 1 -m -p Throughput: 10.89 Mops/s Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <20180910232752.31565-5-cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-09-26qht: drop ht argument from qht iteratorsEmilio G. Cota1-6/+5
Accessing the HT from an iterator results almost always in a deadlock. Given that only one qht-internal function uses this argument, drop it from the interface. Suggested-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-08-23qsp: track BQL callers explicitlyEmilio G. Cota1-0/+6
The BQL is acquired via qemu_mutex_lock_iothread(), which makes the profiler assign the associated wait time (i.e. most of BQL wait time) entirely to that function. This loses the original call site information, which does not help diagnose BQL contention. Fix it by tracking the callers explicitly. Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-23qsp: support call site coalescingEmilio G. Cota1-14/+88
Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-23qsp: add qsp_resetEmilio G. Cota1-0/+94
I first implemented this by deleting all entries in the global hash table. But doing that safely slows down profiling, since we'd need to introduce rcu_read_lock/unlock in the fast path. What's implemented here avoids messing with the thread-local data in the global hash table. It achieves this by taking a snapshot of the current state, so that subsequent reports present the delta wrt to the snapshot. Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-23qsp: add sort_by option to qsp_reportEmilio G. Cota1-6/+27
Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-08-23qsp: QEMU's Synchronization ProfilerEmilio G. Cota1-0/+633
The goal of this module is to profile synchronization primitives (i.e. mutexes, recursive mutexes and condition variables) so that scalability issues can be quickly diagnosed. Sync primitives are profiled by QSP based on the vaddr of the object accessed as well as the call site (file:line_nr). That means the same object called from two different call sites will be tracked in separate entries, which might be reported together or separately (see subsequent commit on call site coalescing). Some perf numbers: Host: Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz Command: taskset -c 0 tests/atomic_add-bench -d 5 -m - Before: 54.80 Mops/s - After: 54.75 Mops/s That is, a negligible slowdown due to the now indirect call to qemu_mutex_lock. Note that using a branch instead of an indirect call introduces a more severe slowdown (53.65 Mops/s, i.e. 2% slowdown). Enabling the profiler (with -p, added in this series) is more interesting: - No profiling: 54.75 Mops/s - W/ profiling: 12.53 Mops/s That is, a 4.36X slowdown. We can break down this slowdown by removing the get_clock calls or the entry lookup: - No profiling: 54.75 Mops/s - W/o get_clock: 25.37 Mops/s - W/o entry lookup: 19.30 Mops/s - W/ profiling: 12.53 Mops/s Signed-off-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
generated by cgit v1.1 at 2025-01-10 05:17:43 +0000