b3998b3bc6
Currently ext4_fc_commit_dentry_updates() is of quadratic time
complexity, which is causing performance bottlenecks with high
threads/file/dir count with fs_mark.
This patch makes commit dentry updates (and hence ext4_fc_commit()) path
to linear time complexity. Hence improves the performance of workloads
which does fsync on multiple threads/open files one-by-one.
Absolute numbers in avg file creates per sec (from fs_mark in 1K order)
=======================================================================
no. Order without-patch(K) with-patch(K) Diff(%)
1 1 16.90 17.51 +3.60
2 2,2 32.08 31.80 -0.87
3 3,3 53.97 55.01 +1.92
4 4,4 78.94 76.90 -2.58
5 5,5 95.82 95.37 -0.46
6 6,6 87.92 103.38 +17.58
7 6,10 0.73 126.13 +17178.08
8 6,14 2.33 143.19 +6045.49
workload type
==============
For e.g. 7th row order of 6,10 (2^6 == 64 && 2^10 == 1024)
echo /run/riteshh/mnt/{1..64} |sed -E 's/[[:space:]]+/ -d /g' \
| xargs -I {} bash -c "sudo fs_mark -L 100 -D 1024 -n 1024 -s0 -S5 -d {}"
Perf profile
(w/o patches)
=============================
87.15% [kernel] [k] ext4_fc_commit --> Heavy contention/bottleneck
1.98% [kernel] [k] perf_event_interrupt
0.96% [kernel] [k] power_pmu_enable
0.91% [kernel] [k] update_sd_lb_stats.constprop.0
0.67% [kernel] [k] ktime_get
Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/930f35d4fd5f83e2673c868781d9ebf15e91bf4e.1645426817.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.