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Sergei Trofimovich
Worked at VirusBlokAda Ltd.
Attended Belarusian State University
Lives in Minsk
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Sergei Trofimovich

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Last weekend was fun: I've spent some time to unbreak pulseaudio on my machine:
    https://bugs.freedesktop.org/show_bug.cgi?id=96873

I happen to use PA over TCP on fresh git kernels. Kernel slightly changed sendmsg()  to be more strict. It started rejecting SCM_CREDENTIALS control message on TCP sockets (pulseaudio wart)

Usermode linux and it's hostfs mount are ideal to validate and bisech that sort of bugs.without any disruption to host kernel.

The proper fix appeared a few hour later I've send an email to kernel devs. And it was Sunday. Amazing!

The fix:
    https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=779f1edec664a7b32b71f7b4702e085a08d60592
Noticed breakage on real applications like mpv and other media apps. PA used to work but I'm not sure what exactly changed in my environment. Currently pulseaudio over TCP is broken on the following versions: 7.1, 8.0, 9.0. How to reproduce: ================= 1. run pulseaudio server on one ...
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Sergei Trofimovich

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Disclaimers, et al. These opinions are not at all related to Arch Linux, though maintaining Arch packages has certainly colored my opinions. I've been a volunteer maintainer for years now, because I feel it helps people. I have a bias towards the value that maintainers and maintaining packages ...
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Sergei Trofimovich

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Ever wondered how 'perf top' looks on haskell programs?

Something like that: http://trofi.github.io/posts/192-perf-on-haskell-programs.html
perf on haskell programs. GHC 7.10.1 got a new -g option to generate debugging information in DWARF format for compiled haskell code. While the -g option was being developed I asked Peter a few times on #ghc how perf top would look like for a random haskell program.
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Erik de Castro Lopo's profile photo
 
This is really interesting +Sergei Trofimovich. I hope there's some patches for GHC coming :).
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Sergei Trofimovich

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Another weekend, another lotz of funz. Guest start is m68k:

http://trofi.github.io/posts/191-ghc-on-m68k.html

GHC on m68k. This all started from this ghc bug report. The bug stated that on m68k ABI return values of int-type are passed in register %d0 while void *-type are passed in register %a0. GHC's C codegen was not using return types consistently. I had zero knowledge of m68k at that time.
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Erik de Castro Lopo's profile photo
 
That's somre really cool hacking Sergi. Congrats!
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Sergei Trofimovich

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PR other/60465 * config/ia64/ia64.c (ia64_expand_load_address): Use gprel64 for local symbolic operands. * config/ia64/predicates.md (local_symbolic_operand64): New predicate. PR othe...
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Ondřej Súkup's profile photoSergei Trofimovich's profile photoАндрэй Захарэвіч's profile photo
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Віншую!
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Sergei Trofimovich

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Did not write anything in a while.

A horror story for you of evil boots and shrunken stacks:
http://trofi.github.io/posts/188-grub-0.97-and-gcc-4.9.html

grub-0.97 and gcc-4.9. Once upon a time (actually the day before yesterday) i dropped an eye at freenode/#gentoo-dev IRC channel and noticed an unusual question: 21:18 <@_AxS_> gcc internals issue.. does anyone happen to know if gcc-4.9 -O2 treats trampolines differently than gcc-4.8 and ...
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I view assembler as a thin layer on top of underlying architecture and operating system which does not require a separate study.

Thus i'd suggest heavyweight but very clear book by Andrew Tanenbaum on common principles of general-purpose processors:

http://www.pearsonhighered.com/educator/product/Structured-Computer-Organization/9780132916523.page

I did read it in russian :)

Once you are familiar with basic concepts you can just read data sheet by hardware vendors.

Example one from Intel: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html

This one while being huge is nicely structured and contains all sorts of details. From basic computation model decription (register types, fancy modes of operation, FPU modes, etc.) to pseudocode for every instruction and more.

Of more advanced tricks i'd suggest to look at some docs from Agner Fog:

http://agner.org/optimize/#manuals

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Sergei Trofimovich

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Yeah, that was some really good work by +Neil Mitchell !
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Sergei Trofimovich

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An update on my 2014 report.
New GCC is just around the corner. For me, as a GCC developer, this means a period of bugfixing, benchmarking and fine-tuning. Two years ago I wrote about my experiment of building libreoffice with link time optimization (LT...
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Sergei Trofimovich

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Add flag to optionally ignore ELF interposition. From: Jan Hubicka ; To: gcc-patches at gcc dot gnu dot org; Date: Tue, 20 May 2014 22:04:32 +0200; Subject: Add flag to optionally ignore ELF interposition; Authentication-results: sourceware.org; auth=none ...
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Sergei Trofimovich

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glibc on ia64 or how relocations bootstrap. It was a rainy evening on #gentoo-ia64 and suddenly 00:40 < undersys> trying out glibc 2.21 on my ia64 box 00:41 < undersys> all compiles fine, gets to preinstall test and fails 00:41 < undersys> "simple run test (/usr/bin/cal) failed" wat :C ..
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Interesting read, hairy horror story :)
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Have him in circles
109 people
Дмитрий Бушенко's profile photo
Mikle Kolyada's profile photo
Ulrich Müller's profile photo
Garbar Anton's profile photo
Сергей Исаченко's profile photo
Yegor Yefremov's profile photo
W Whatever's profile photo
Виктория Мамаева's profile photo
Gentoo's profile photo
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  • VirusBlokAda Ltd.
    Very Serious Guy, 2006 - 2014
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bit master
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gentoo, haskell, c, exotic arches, natural languages.
snowboarding, (folk) music and more!
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  • Belarusian State University
    Radiophysics, 2002 - 2007
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