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8cd115bdda
Currently we start transaction for mapping every extent for writing using direct IO. This is unnecessary when we know we are overwriting already allocated blocks and the overhead of starting a transaction can be significant especially for multithreaded workloads doing small writes. Use iomap operations that avoid starting a transaction for direct IO overwrites. This improves throughput of 4k random writes - fio jobfile: [global] rw=randrw norandommap=1 invalidate=0 bs=4k numjobs=16 time_based=1 ramp_time=30 runtime=120 group_reporting=1 ioengine=psync direct=1 size=16G filename=file1.0.0:file1.0.1:file1.0.2:file1.0.3:file1.0.4:file1.0.5:file1.0.6:file1.0.7:file1.0.8:file1.0.9:file1.0.10:file1.0.11:file1.0.12:file1.0.13:file1.0.14:file1.0.15:file1.0.16:file1.0.17:file1.0.18:file1.0.19:file1.0.20:file1.0.21:file1.0.22:file1.0.23:file1.0.24:file1.0.25:file1.0.26:file1.0.27:file1.0.28:file1.0.29:file1.0.30:file1.0.31 file_service_type=random nrfiles=32 from 3018MB/s to 4059MB/s in my test VM running test against simulated pmem device (note that before iomap conversion, this workload was able to achieve 3708MB/s because old direct IO path avoided transaction start for overwrites as well). For dax, the win is even larger improving throughput from 3042MB/s to 4311MB/s. Reported-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20191218174433.19380-1-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
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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.