linux-kernel - Re: [PATCH] mm, vmscan, tracing: Use pointer to reclaim

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Date:   Thu, 22 Mar 2018 13:03:13 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Michal Hocko <mhocko@...e.com>, Mel Gorman <mgorman@...e.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexei Starovoitov <ast@...com>
Subject: Re: [PATCH] mm, vmscan, tracing: Use pointer to reclaim_stat struct
 in trace event

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@fb.com
> 
> Reported-by: Alexei Starovoitov <ast@...com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Acked-by: David Rientjes <rientjes@...gle.com>