linux-kernel - [PATCH v2 0/3] lib/list_batch: A simple list insertion/deletion batching facility

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Date:	Fri, 29 Jan 2016 14:30:43 -0500
From:	Waiman Long <Waiman.Long@....com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>,
	Waiman Long <Waiman.Long@....com>
Subject: [PATCH v2 0/3] lib/list_batch: A simple list insertion/deletion batching facility

v1->v2:
  - Address feedbacks from PeterZ and Andi Kleen.

This patchset introduces a simple list insertion/deletion batching
facility to batch multiple list insertion and deletion operations
into a single one under one lock/unlock critical section.

Patch 1 introduces this new facility.

Patch 2 enables it for the x86 architecture.

Patch 3 makes the insertion and deletion of the VFS superblock's
inode list to use the new list batching functions.

On x86-64, the generated code (gcc v4.8.5) of the inode_sb_list_add()
function without the patch was:

   0x0000000000001030 <+0>:     callq  0x1035 <inode_sb_list_add+5>
   0x0000000000001035 <+5>:     push   %rbp
   0x0000000000001036 <+6>:     mov    %rsp,%rbp
   0x0000000000001039 <+9>:     push   %rbx
   0x000000000000103a <+10>:    mov    0x28(%rdi),%rax
   0x000000000000103e <+14>:    mov    %rdi,%rbx
   0x0000000000001041 <+17>:    lea    0x600(%rax),%rdi
   0x0000000000001048 <+24>:    callq  0x104d <inode_sb_list_add+29>
   0x000000000000104d <+29>:    mov    0x28(%rbx),%rsi
   0x0000000000001051 <+33>:    lea    0x120(%rbx),%rdi
   0x0000000000001058 <+40>:    mov    0x608(%rsi),%rdx
   0x000000000000105f <+47>:    add    $0x608,%rsi
   0x0000000000001066 <+54>:    callq  0x106b <inode_sb_list_add+59>
   0x000000000000106b <+59>:    mov    0x28(%rbx),%rdi
   0x000000000000106f <+63>:    add    $0x600,%rdi
   0x0000000000001076 <+70>:    callq  *0x0
   0x000000000000107d <+77>:    pop    %rbx
   0x000000000000107e <+78>:    pop    %rbp
   0x000000000000107f <+79>:    retq

With the patch, the function became:

   0x0000000000001030 <+0>:     callq  0x1035 <inode_sb_list_add+5>
   0x0000000000001035 <+5>:     push   %rbp
   0x0000000000001036 <+6>:     mov    %rsp,%rbp
   0x0000000000001039 <+9>:     push   %r13
   0x000000000000103b <+11>:    lea    0x120(%rdi),%r13
   0x0000000000001042 <+18>:    push   %r12
   0x0000000000001044 <+20>:    push   %rbx
   0x0000000000001045 <+21>:    mov    0x28(%rdi),%r12
   0x0000000000001049 <+25>:    lea    0x600(%r12),%rbx
   0x0000000000001051 <+33>:    mov    %rbx,%rdi
   0x0000000000001054 <+36>:    callq  0x1059 <inode_sb_list_add+41>
   0x0000000000001059 <+41>:    test   %eax,%eax
   0x000000000000105b <+43>:    je     0x1081 <inode_sb_list_add+81>
   0x000000000000105d <+45>:    mov    0x618(%r12),%rsi
   0x0000000000001065 <+53>:    mov    %r13,%rdi
   0x0000000000001068 <+56>:    mov    (%rsi),%rdx
   0x000000000000106b <+59>:    callq  0x1070 <inode_sb_list_add+64>
   0x0000000000001070 <+64>:    mov    %rbx,%rdi
   0x0000000000001073 <+67>:    callq  *0x0
   0x000000000000107a <+74>:    pop    %rbx
   0x000000000000107b <+75>:    pop    %r12
   0x000000000000107d <+77>:    pop    %r13
   0x000000000000107f <+79>:    pop    %rbp
   0x0000000000001080 <+80>:    retq
   0x0000000000001081 <+81>:    lea    0x618(%r12),%rdx
   0x0000000000001089 <+89>:    mov    %r13,%rcx
   0x000000000000108c <+92>:    mov    %rbx,%rsi
   0x000000000000108f <+95>:    xor    %edi,%edi
   0x0000000000001091 <+97>:    callq  0x1096 <inode_sb_list_add+102>
   0x0000000000001096 <+102>:   jmp    0x107a <inode_sb_list_add+74>

For the fastpath, the only overheads are the testing of the return value
of the spin_trylock function and the push/pop of 2 more registers. Other
than that, they look very similar.

Waiman Long (3):
  lib/list_batch: A simple list insertion/deletion batching facility
  lib/list_batch, x86: Enable list insertion/deletion batching for x86
  vfs: Enable list batching for the superblock's inode list

 arch/x86/Kconfig           |    1 +
 fs/inode.c                 |   13 ++---
 fs/super.c                 |    1 +
 include/linux/fs.h         |    2 +
 include/linux/list_batch.h |  133 ++++++++++++++++++++++++++++++++++++++++++++
 lib/Kconfig                |    7 ++
 lib/Makefile               |    1 +
 lib/list_batch.c           |  125 +++++++++++++++++++++++++++++++++++++++++
 8 files changed, 275 insertions(+), 8 deletions(-)
 create mode 100644 include/linux/list_batch.h
 create mode 100644 lib/list_batch.c