[PATCH v3 0/2] ext4: increase mbcache scalability

[T Makphaibulchoke]

This patch intends to improve the scalability of an ext filesystem,
particularly ext4.

The patch consists of two parts.  The first part introduces higher degree of
parallelism to the usages of the mb_cache and mb_cache_entries and impacts
all ext filesystems.

The second part of the patch further increases the scalablity of an ext4
filesystem by having each ext4 fielsystem allocate and use its own private
mbcache structure, instead of sharing a single mcache structures across all
ext4 filesystems

Here are some of the benchmark results with the changes. 

On a 90 core machine:

Here are the performance improvements in some of the aim7 workloads,

---------------------------
|             | % increase |
---------------------------
| alltests    |     11.85  |
---------------------------
| custom      |     14.42  |
---------------------------
| fserver     |     21.36  |  
---------------------------
| new_dbase   |      5.59 |  
---------------------------
| new_fserver |     21.45  |  
---------------------------
| shared      |     12.84  |  
---------------------------
For Swingbench dss workload, with 16 GB database,

-------------------------------------------------------------------------------
| Users        | 100  | 200  | 300  | 400  | 500  | 600  | 700  | 800  | 900  |
-------------------------------------------------------------------------------
| % imprvoment | 8.46 | 8.00 | 7.35 | -.313| 1.09 | 0.69 | 0.30 | 2.18 | 5.23 |
-------------------------------------------------------------------------------
| % imprvoment |45.66 |47.62 |34.54 |25.15 |15.29 | 3.38 | -8.7 |-4.98 |-7.86 |
| without using|      |      |      |      |      |      |      |      |      |
| shared memory|      |      |      |      |      |      |      |      |      |
-------------------------------------------------------------------------------
For SPECjbb2013, composite run,

--------------------------------------------
|               | max-jOPS | critical-jOPS |
--------------------------------------------
| % improvement |   5.99   |     N/A       |
--------------------------------------------


On an 80 core machine:

The aim7's results for most of the workloads turn out to the same.

Here are the results of Swingbench dss workload,

-------------------------------------------------------------------------------
| Users        | 100  | 200  | 300  | 400  | 500  | 600  | 700  | 800  | 900  |
-------------------------------------------------------------------------------
| % imprvoment |-1.79 | 0.37 | 1.36 | 0.08 | 1.66 | 2.09 | 1.16 | 1.48 | 1.92 |
-------------------------------------------------------------------------------

The changes have been tested with ext4 xfstests to verify that no regression
has been introduced. 

Changed in v3:
	- New diff summary

Changed in v2:
	- New performance data
	- New diff summary

T Makphaibulchoke (2):
  mbcache: decoupling the locking of local from global data
  ext4: each filesystem creates and uses its own mb_cache

 fs/ext4/ext4.h          |   1 +
 fs/ext4/super.c         |  24 ++--
 fs/ext4/xattr.c         |  51 ++++----
 fs/ext4/xattr.h         |   6 +-
 fs/mbcache.c            | 306 +++++++++++++++++++++++++++++++++++-------------
 include/linux/mbcache.h |  10 +-
 6 files changed, 277 insertions(+), 121 deletions(-)

-- 
1.7.11.3

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