Re: bin/50638: Extreme slowness on loading gzipped kernels on old CPUs

[Kamil Rytarowski <n54%gmx.com@localhost>]

The following reply was made to PR bin/50638; it has been noted by GNATS.

From: Kamil Rytarowski <n54%gmx.com@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: bin/50638: Extreme slowness on loading gzipped kernels on old
 CPUs
Date: Sun, 10 Jan 2016 22:18:27 +0100

 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA256
 
 On 10.01.2016 19:06, Joerg Sonnenberger wrote:
 > On Sun, Jan 10, 2016 at 05:40:00PM +0000, Izumi Tsutsui wrote:
 >> (1) leave as is and use the dumb crc32() function (for small
 >> binary) (2) pull "DYNAMIC_CRC_TABLE" implementation from zlib
 >> into libkern/crc32.c (3) completely disable gunzip crc32()
 >> calculation in cread() function
 > 
 > Another option would be to use a version of what libarchive is
 > using in 
 > src/external/bsd/libarchive/dist/libarchive/archive_crc32.h. That 
 > version is still pretty small.
 > 
 
 Just a note. Recent x86_64 and optionally armv8 ships with intrinsic
 functions implemented in their cores for CRC32 functions.
 
 According to my tests the lookup algorithm is 3-4x slower on x86_64
 and armv8 than a function reusing the dedicated CPU instruction.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v2
 
 iQIcBAEBCAAGBQJWksqhAAoJEEuzCOmwLnZst2UP/0FuXiM1/mhU1G0hawqEAdeh
 /POd5Od0sZpkHGmeK6lJRSWUN3ZmXg5oyIAH9EExbpCH2IueZMOYnSWRLS1MsTbB
 /iAe+MNWk7li/VlM3i947wZ2Tzsz8gs5Ar/E9OEsF2Vno6HDs0djp6tIOeB1OUS2
 V/XYmzbomGuIrkjT5aluIz5aTq/0yVWOOcL4YQw3nWfJWJWzThZ0tr7u3teylEgZ
 OVnE7PLJQjyGysZ7jzTaPoByjuOINVmM3Bn924X1X4UmuEPkOSRTql40C8yac+Nk
 bkl636JR6og+VDrbKnOBkkXMDfQlKO01sefWj4YjkWjJmNr7jmgYzlR1d1QaXvKr
 3prHt9pIjLM9Y+7fy6OFMMLXVk/euvaHbuw2G+yfvoMt/6ll+CXtIAvh1DHQRcu0
 Jw+czWYMWoYMRBc79zCiXbgDDHZVXob+DQD9QlhK7IRuHxOpfnwAm1mJhLB03MHq
 wJyHBxwvlqBelLi10ZnKOIIOebVA/n3HYpMBN5QyLs2aYT1v1IhtOceP3yko699w
 E0PHxVksWekatid4YSBV6rqS/krrsYg154hwOYVvLQzRe5voMHZo6FIzvSYTkeL3
 3zbLtH5opYA+iA+R94h+RJ2k+Kl9icrND3Fr7GNmDNHiswkNkGchVMC2cR5Rcyl4
 d9FQbFAi68/Q0BWcRFzo
 =e7dy
 -----END PGP SIGNATURE-----