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Message-ID: <20171220215914.GA7877@avx2>
Date: Thu, 21 Dec 2017 00:59:14 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] proc: rearrange struct proc_dir_entry
struct proc_dir_entry became bit messy over years:
* move 16-bit ->mode_t before namelen to get rid of padding
* make ->in_use first field: it seems to be most used resulting in
smaller code on x86_64 (defconfig):
add/remove: 0/0 grow/shrink: 7/13 up/down: 24/-67 (-43)
Function old new delta
proc_readdir_de 451 455 +4
proc_get_inode 282 286 +4
pde_put 65 69 +4
remove_proc_subtree 294 297 +3
remove_proc_entry 297 300 +3
proc_register 295 298 +3
proc_notify_change 94 97 +3
unuse_pde 27 26 -1
proc_reg_write 89 85 -4
proc_reg_unlocked_ioctl 85 81 -4
proc_reg_read 89 85 -4
proc_reg_llseek 87 83 -4
proc_reg_get_unmapped_area 123 119 -4
proc_entry_rundown 139 135 -4
proc_reg_poll 91 85 -6
proc_reg_mmap 79 73 -6
proc_get_link 55 49 -6
proc_reg_release 108 101 -7
proc_reg_open 298 291 -7
close_pdeo 228 218 -10
* move writeable fields together to a first cacheline (on x86_64),
those include
* ->in_use: reference count, taken every open/read/write/close etc
* ->count: reference count, taken at readdir on every entry
* ->pde_openers: tracks (nearly) every open, dirtied
* ->pde_unload_lock: spinlock protecting ->pde_openers
* ->proc_iops, ->proc_fops, ->data: writeonce fields,
used right together with previous group.
* other rarely written fields go into 1st/2nd and 2nd/3rd cacheline on
32-bit and 64-bit respectively.
Additionally on 32-bit, ->subdir, ->subdir_node, ->namelen, ->name
go fully into 2nd cacheline, separated from writeable fields.
They are all used during lookup.
Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
fs/proc/internal.h | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -31,24 +31,27 @@ struct mempolicy;
* subdir_node is used to build the rb tree "subdir" of the parent.
*/
struct proc_dir_entry {
+ /*
+ * number of callers into module in progress;
+ * negative -> it's going away RSN
+ */
+ atomic_t in_use;
+ atomic_t count; /* use count */
+ struct list_head pde_openers; /* who did ->open, but not ->release */
+ spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
+ struct completion *pde_unload_completion;
+ const struct inode_operations *proc_iops;
+ const struct file_operations *proc_fops;
+ void *data;
unsigned int low_ino;
- umode_t mode;
nlink_t nlink;
kuid_t uid;
kgid_t gid;
loff_t size;
- const struct inode_operations *proc_iops;
- const struct file_operations *proc_fops;
struct proc_dir_entry *parent;
struct rb_root_cached subdir;
struct rb_node subdir_node;
- void *data;
- atomic_t count; /* use count */
- atomic_t in_use; /* number of callers into module in progress; */
- /* negative -> it's going away RSN */
- struct completion *pde_unload_completion;
- struct list_head pde_openers; /* who did ->open, but not ->release */
- spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
+ umode_t mode;
u8 namelen;
char name[];
} __randomize_layout;
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