* [PATCH v2] fs: shave 8 bytes off of struct inode
@ 2018-07-05 6:25 Amir Goldstein
0 siblings, 0 replies; only message in thread
From: Amir Goldstein @ 2018-07-05 6:25 UTC (permalink / raw)
To: Al Viro
Cc: Linus Torvalds, Jan Kara, kernel test robot, LKP, linux-fsdevel,
linux-kernel
Here is a link to Linus' reply to Jan's concern about making
i_blkbibts byte addressable:
https://marc.info/?l=linux-fsdevel&m=152882624707975&w=2
Here is a link to an lkp.org report about potential performance
improvement in some workload, which could(?) be related to packing
i_blkbits closer to i_bytes/i_lock:
https://marc.info/?l=linux-fsdevel&m=153077048108198&w=2
Changes since v1:
- Add links to relevant discussions
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
Al,
Re-posting the patch per your request.
Regarding your question:
"I would like more details about the variation of timing -
what's the dispersion from boot to boot, for starters?"
I haven't run those performance tests, just got them from lkp robot,
so perhaps Xiaolong can answer your question.
I too, find the reported improvement a bit too good to be reliably
true. I do see in the graphs at the bottom of the report that there
are many good vs. bad samples though.
Thanks,
Amir.
include/linux/fs.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 760d8da1b6c7..6d0489613dc1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -274,6 +274,7 @@ struct writeback_control;
/*
* Write life time hint values.
+ * Stored in struct inode as u8.
*/
enum rw_hint {
WRITE_LIFE_NOT_SET = 0,
@@ -607,8 +608,8 @@ struct inode {
struct timespec i_ctime;
spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
unsigned short i_bytes;
- unsigned int i_blkbits;
- enum rw_hint i_write_hint;
+ u8 i_blkbits;
+ u8 i_write_hint;
blkcnt_t i_blocks;
#ifdef __NEED_I_SIZE_ORDERED
--
2.7.4
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