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Mikulas Patocka
dcd195071f
When dm-writecache is used with SSD as a cache device, it would submit a
separate bio for each written block. The I/Os would be merged by the disk
scheduler, but this merging degrades performance.
Improve dm-writecache performance by submitting larger bios - this is
possible as long as there is consecutive free space on the cache
device.
Benchmark (arm64 with 64k page size, using /dev/ram0 as a cache device):
fio --bs=512k --iodepth=32 --size=400M --direct=1 \
--filename=/dev/mapper/cache --rw=randwrite --numjobs=1 --name=test
block old new
size MiB/s MiB/s
---------------------
512 181 700
1k 347 1256
2k 644 2020
4k 1183 2759
8k 1852 3333
16k 2469 3509
32k 2974 3670
64k 3404 3810
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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
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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
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the problems which may result by upgrading your kernel.