mirror of
https://gitee.com/bianbu-linux/linux-6.6
synced 2025-04-24 14:07:52 -04:00
a381b70a1c
According to Kees's suggest, we started with the patch that just replaces
rmb() with smp_rmb() and did a performance test with UnixBench. The
results showed the overhead about 2.53% in rmb() test compared to the
smp_rmb() one, in a x86-64 kernel with CONFIG_SMP enabled running inside a
qemu-kvm vm. The test is a "syscall" testcase in UnixBench, which executes
5 syscalls in a loop during a certain timeout (100 second in our test) and
counts the total number of executions of this 5-syscall sequence. We set
a seccomp filter with all allow rule for all used syscalls in this test
(which will go bitmap path) to make sure the rmb() will be executed. The
details for the test:
with rmb():
/txm # ./syscall_allow_min 100
COUNT|35861159|1|lps
/txm # ./syscall_allow_min 100
COUNT|35545501|1|lps
/txm # ./syscall_allow_min 100
COUNT|35664495|1|lps
with smp_rmb():
/txm # ./syscall_allow_min 100
COUNT|36552771|1|lps
/txm # ./syscall_allow_min 100
COUNT|36491247|1|lps
/txm # ./syscall_allow_min 100
COUNT|36504746|1|lps
For a x86-64 kernel with CONFIG_SMP enabled, the smp_rmb() is just a
compiler barrier() which have no impact in runtime, while rmb() is a
lfence which will prevent all memory access operations (not just load
according the recently claim by Intel) behind itself. We can also figure
it out in disassembly:
with rmb():
0000000000001430 <__seccomp_filter>:
1430: 41 57 push %r15
1432: 41 56 push %r14
1434: 41 55 push %r13
1436: 41 54 push %r12
1438: 55 push %rbp
1439: 53 push %rbx
143a: 48 81 ec 90 00 00 00 sub $0x90,%rsp
1441: 89 7c 24 10 mov %edi,0x10(%rsp)
1445: 89 54 24 14 mov %edx,0x14(%rsp)
1449: 65 48 8b 04 25 28 00 mov %gs:0x28,%rax
1450: 00 00
1452: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
1459: 00
145a: 31 c0 xor %eax,%eax
* 145c: 0f ae e8 lfence
145f: 48 85 f6 test %rsi,%rsi
1462: 49 89 f4 mov %rsi,%r12
1465: 0f 84 42 03 00 00 je 17ad <__seccomp_filter+0x37d>
146b: 65 48 8b 04 25 00 00 mov %gs:0x0,%rax
1472: 00 00
1474: 48 8b 98 80 07 00 00 mov 0x780(%rax),%rbx
147b: 48 85 db test %rbx,%rbx
with smp_rmb();
0000000000001430 <__seccomp_filter>:
1430: 41 57 push %r15
1432: 41 56 push %r14
1434: 41 55 push %r13
1436: 41 54 push %r12
1438: 55 push %rbp
1439: 53 push %rbx
143a: 48 81 ec 90 00 00 00 sub $0x90,%rsp
1441: 89 7c 24 10 mov %edi,0x10(%rsp)
1445: 89 54 24 14 mov %edx,0x14(%rsp)
1449: 65 48 8b 04 25 28 00 mov %gs:0x28,%rax
1450: 00 00
1452: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
1459: 00
145a: 31 c0 xor %eax,%eax
145c: 48 85 f6 test %rsi,%rsi
145f: 49 89 f4 mov %rsi,%r12
1462: 0f 84 42 03 00 00 je 17aa <__seccomp_filter+0x37a>
1468: 65 48 8b 04 25 00 00 mov %gs:0x0,%rax
146f: 00 00
1471: 48 8b 98 80 07 00 00 mov 0x780(%rax),%rbx
1478: 48 85 db test %rbx,%rbx
Signed-off-by: wanghongzhe <wanghongzhe@huawei.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/1612496049-32507-1-git-send-email-wanghongzhe@huawei.com
|
||
|---|---|---|
| .. | ||
| bpf | ||
| cgroup | ||
| configs | ||
| debug | ||
| dma | ||
| entry | ||
| events | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| acct.c | ||
| async.c | ||
| audit.c | ||
| audit.h | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu.c | ||
| cpu_pm.c | ||
| crash_core.c | ||
| crash_dump.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fail_function.c | ||
| fork.c | ||
| freezer.c | ||
| futex.c | ||
| gen_kheaders.sh | ||
| groups.c | ||
| hung_task.c | ||
| iomem.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kcmp.c | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| kcov.c | ||
| kexec.c | ||
| kexec_core.c | ||
| kexec_elf.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kheaders.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| Makefile | ||
| module-internal.h | ||
| module.c | ||
| module_signature.c | ||
| module_signing.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid.c | ||
| pid_namespace.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| regset.c | ||
| relay.c | ||
| resource.c | ||
| resource_kunit.c | ||
| rseq.c | ||
| scftorture.c | ||
| scs.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stackleak.c | ||
| stacktrace.c | ||
| static_call.c | ||
| stop_machine.c | ||
| sys.c | ||
| sys_ni.c | ||
| sysctl-test.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| ucount.c | ||
| uid16.c | ||
| uid16.h | ||
| umh.c | ||
| up.c | ||
| user-return-notifier.c | ||
| user.c | ||
| user_namespace.c | ||
| usermode_driver.c | ||
| utsname.c | ||
| utsname_sysctl.c | ||
| watch_queue.c | ||
| watchdog.c | ||
| watchdog_hld.c | ||
| workqueue.c | ||
| workqueue_internal.h | ||