4fc55e3e46
o Split the compression across several worker threads. By default, "several" matches number of CPUs, capped at 24 for sanity when running on a very big hardwares. Provide option to set that number manually; o Fix bug inherited from the mkulzma (R.I.P) which degraded already slow LZMA compression even further by calling function to release compression state after processing each block. It is neither documented as required nor actually required by the LZMA library. This caused spree of system calls to release memory and then map it again for every block. LZMA compression is more than 2x faster after this change alone; o Record time it takes to do compression and report throughput achieved. o Add simple first-level 256 entry hash table for de-dup code, so it's not becoming a bottleneck at big files.
186 lines
5.4 KiB
Groff
186 lines
5.4 KiB
Groff
.\"-
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.\" Copyright (c) 2004-2016 Maxim Sobolev <sobomax@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 17, 2006
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.Dt MKUZIP 8
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.Os
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.Sh NAME
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.Nm mkuzip
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.Nd compress disk image for use with
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.Xr geom_uzip 4
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class
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.Sh SYNOPSIS
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.Nm
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.Op Fl v
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.Op Fl o Ar outfile
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.Op Fl s Ar cluster_size
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.Op Fl j Ar compression_jobs
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.Ar infile
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.Sh DESCRIPTION
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The
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.Nm
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utility compresses a disk image file so that the
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.Xr geom_uzip 4
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class will be able to decompress the resulting image at run-time.
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This allows for a significant reduction of size of disk image at
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the expense of some CPU time required to decompress the data each
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time it is read.
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The
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.Nm
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utility
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works in two phases:
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.Bl -enum
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.It
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An
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.Ar infile
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image is split into clusters; each cluster is compressed using
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.Xr zlib 3
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or
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.Xr lzma 3 .
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.It
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The resulting set of compressed clusters along with headers that allow
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locating each individual cluster is written to the output file.
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.El
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.Pp
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The options are:
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.Bl -tag -width indent
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.It Fl o Ar outfile
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Name of the output file
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.Ar outfile .
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The default is to use the input name with the suffix
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.Pa .uzip
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for the
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.Xr zlib 3
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compression or
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.Pa .ulzma
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for the
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.Xr lzma 3 .
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.It Fl L
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Use
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.Xr lzma 3
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compression algorithm instead of the default
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.Xr zlib 3 .
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The
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.Xr lzma 3
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provides noticeable better compression levels on the same data set
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at the expense of much slower compression speed (10-20x) and somewhat slower
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decompression (2-3x).
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.It Fl s Ar cluster_size
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Split the image into clusters of
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.Ar cluster_size
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bytes, 16384 bytes by default.
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The
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.Ar cluster_size
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should be a multiple of 512 bytes.
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.It Fl v
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Display verbose messages.
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.It Fl Z
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Disable zero-blocks detection and elimination.
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When this option is set, the
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.Nm
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would compress empty blocks (i.e. clusters that consist of only zero bytes)
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just as it would any other block.
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When the option is not set, the
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.Nm
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detects such blocks and skips them from the output.
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Setting
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.Fl Z
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results is slight increase of compressed image size, typically less than 0.1%
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of a final size of the compressed image.
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.It Fl d
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Enable de-duplication.
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When the option is enabled the
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.Nm
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detects identical blocks in the input and replaces each subsequent occurence
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of such block with pointer to the very first one in the output.
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Setting this option results is moderate decrease of compressed image size,
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typically around 3-5% of a final size of the compressed image.
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.It Fl S
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Print summary about the compression ratio as well as output
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file size after file has been processed.
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.It Fl j Ar compression_jobs
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Specify the number of compression jobs that
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.Nm
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runs in parallel to speed up compression.
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When option is not specified the number of jobs set to be equal
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to the value of
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.Va hw.ncpu
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.Xr sysctl 8
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variable.
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.El
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.Sh NOTES
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The compression ratio largely depends on the cluster size used.
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.\" The following two sentences are unclear: how can gzip(1) be
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.\" used in a comparable fashion, and wouldn't a gzip-compressed
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.\" image suffer from larger cluster sizes as well?
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For large cluster sizes (16K and higher), typical compression ratios
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are only 1-2% less than those achieved with
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.Xr gzip 1 .
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However, it should be kept in mind that larger cluster
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sizes lead to higher overhead in the
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.Xr geom_uzip 4
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class, as the class has to decompress the whole cluster even if
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only a few bytes from that cluster have to be read.
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.Pp
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The
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.Nm
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utility
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inserts a short shell script at the beginning of the generated image,
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which makes it possible to
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.Dq run
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the image just like any other shell script.
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The script tries to load the
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.Xr geom_uzip 4
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class if it is not loaded, configure the image as an
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.Xr md 4
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disk device using
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.Xr mdconfig 8 ,
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and automatically mount it using
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.Xr mount_cd9660 8
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on the mount point provided as the first argument to the script.
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.Pp
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The de-duplication is a
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.Fx
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specific feature and while it does not require any changes to on-disk
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compressed image format, however it did require some matching changes to the
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.Xr geom_uzip 4
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to handle resulting images correctly.
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.Sh EXIT STATUS
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.Ex -std
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.Sh SEE ALSO
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.Xr gzip 1 ,
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.Xr xz 1 ,
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.Xr zlib 3 ,
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.Xr lzma 3 ,
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.Xr geom 4 ,
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.Xr geom_uzip 4 ,
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.Xr md 4 ,
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.Xr mdconfig 8 ,
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.Xr mount_cd9660 8
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.Sh AUTHORS
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.An Maxim Sobolev Aq Mt sobomax@FreeBSD.org
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