Re: [PATCH] mm, vmscan, tracing: Use pointer to reclaim_stat struct in trace event

From: David Rientjes
Date: Thu Mar 22 2018 - 16:03:22 EST


On Thu, 22 Mar 2018, Steven Rostedt wrote:

>
> The trace event trace_mm_vmscan_lru_shrink_inactive() currently has 12
> parameters! Seven of them are from the reclaim_stat structure. This
> structure is currently local to mm/vmscan.c. By moving it to the global
> vmstat.h header, we can also reference it from the vmscan tracepoints. In
> moving it, it brings down the overhead of passing so many arguments to the
> trace event. In the future, we may limit the number of arguments that a
> trace event may pass (ideally just 6, but more realistically it may be 8).
>
> Before this patch, the code to call the trace event is this:
>
> 0f 83 aa fe ff ff jae ffffffff811e6261 <shrink_inactive_list+0x1e1>
> 48 8b 45 a0 mov -0x60(%rbp),%rax
> 45 8b 64 24 20 mov 0x20(%r12),%r12d
> 44 8b 6d d4 mov -0x2c(%rbp),%r13d
> 8b 4d d0 mov -0x30(%rbp),%ecx
> 44 8b 75 cc mov -0x34(%rbp),%r14d
> 44 8b 7d c8 mov -0x38(%rbp),%r15d
> 48 89 45 90 mov %rax,-0x70(%rbp)
> 8b 83 b8 fe ff ff mov -0x148(%rbx),%eax
> 8b 55 c0 mov -0x40(%rbp),%edx
> 8b 7d c4 mov -0x3c(%rbp),%edi
> 8b 75 b8 mov -0x48(%rbp),%esi
> 89 45 80 mov %eax,-0x80(%rbp)
> 65 ff 05 e4 f7 e2 7e incl %gs:0x7ee2f7e4(%rip) # 15bd0 <__preempt_count>
> 48 8b 05 75 5b 13 01 mov 0x1135b75(%rip),%rax # ffffffff8231bf68 <__tracepoint_mm_vmscan_lru_shrink_inactive+0x28>
> 48 85 c0 test %rax,%rax
> 74 72 je ffffffff811e646a <shrink_inactive_list+0x3ea>
> 48 89 c3 mov %rax,%rbx
> 4c 8b 10 mov (%rax),%r10
> 89 f8 mov %edi,%eax
> 48 89 85 68 ff ff ff mov %rax,-0x98(%rbp)
> 89 f0 mov %esi,%eax
> 48 89 85 60 ff ff ff mov %rax,-0xa0(%rbp)
> 89 c8 mov %ecx,%eax
> 48 89 85 78 ff ff ff mov %rax,-0x88(%rbp)
> 89 d0 mov %edx,%eax
> 48 89 85 70 ff ff ff mov %rax,-0x90(%rbp)
> 8b 45 8c mov -0x74(%rbp),%eax
> 48 8b 7b 08 mov 0x8(%rbx),%rdi
> 48 83 c3 18 add $0x18,%rbx
> 50 push %rax
> 41 54 push %r12
> 41 55 push %r13
> ff b5 78 ff ff ff pushq -0x88(%rbp)
> 41 56 push %r14
> 41 57 push %r15
> ff b5 70 ff ff ff pushq -0x90(%rbp)
> 4c 8b 8d 68 ff ff ff mov -0x98(%rbp),%r9
> 4c 8b 85 60 ff ff ff mov -0xa0(%rbp),%r8
> 48 8b 4d 98 mov -0x68(%rbp),%rcx
> 48 8b 55 90 mov -0x70(%rbp),%rdx
> 8b 75 80 mov -0x80(%rbp),%esi
> 41 ff d2 callq *%r10
>
> After the patch:
>
> 0f 83 a8 fe ff ff jae ffffffff811e626d <shrink_inactive_list+0x1cd>
> 8b 9b b8 fe ff ff mov -0x148(%rbx),%ebx
> 45 8b 64 24 20 mov 0x20(%r12),%r12d
> 4c 8b 6d a0 mov -0x60(%rbp),%r13
> 65 ff 05 f5 f7 e2 7e incl %gs:0x7ee2f7f5(%rip) # 15bd0 <__preempt_count>
> 4c 8b 35 86 5b 13 01 mov 0x1135b86(%rip),%r14 # ffffffff8231bf68 <__tracepoint_mm_vmscan_lru_shrink_inactive+0x28>
> 4d 85 f6 test %r14,%r14
> 74 2a je ffffffff811e6411 <shrink_inactive_list+0x371>
> 49 8b 06 mov (%r14),%rax
> 8b 4d 8c mov -0x74(%rbp),%ecx
> 49 8b 7e 08 mov 0x8(%r14),%rdi
> 49 83 c6 18 add $0x18,%r14
> 4c 89 ea mov %r13,%rdx
> 45 89 e1 mov %r12d,%r9d
> 4c 8d 45 b8 lea -0x48(%rbp),%r8
> 89 de mov %ebx,%esi
> 51 push %rcx
> 48 8b 4d 98 mov -0x68(%rbp),%rcx
> ff d0 callq *%rax
>
> Link: http://lkml.kernel.org/r/2559d7cb-ec60-1200-2362-04fa34fd02bb@xxxxxx
>
> Reported-by: Alexei Starovoitov <ast@xxxxxx>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>