Estou procurando apenas alguns poucos usuários Linode 64 atualmente em hosts no datacenter Fremont (host9 e superior) para ajudar a testar um novo patch de desempenho para o host e UML.
UML funciona usando ptrace, uma função do Linux para interceptar chamadas de sistema feitas por aplicações. Quando seu UML faz uma chamada de sistema, o host intercepta a chamada, executa o trabalho dentro do UML e null-ifica a chamada de sistema no host convertendo essa chamada de sistema para "ficar estúpido" no host. O problema com isto é que ele gera duas trocas de contexto no host.
Com a [url=http://perso.wanadoo.fr/laurent.vivier/UML/
A partir do momento em que o sistema de controle de contexto é instalado no host e na UML, ele não se preocupa em rodar "ficar estúpido", reduzindo assim o número de trocas de contexto de 2 para 1.
[b]Benchmarks[/b]
Aqui estão algumas referências do "mundo real" usando o roteiro de testes de execução do Mysql:
http://www.theshore.net/~caker/uml/sysemu-benchmarks.txt
Em resumo, os testes correram [b]33% mais rápido[/b] do que sem as correções do sysemu.
[b]Detalhes[/b]
[lista][*] Migraremos você para o host25, mantendo reservado seu slot no host anterior (no caso de precisarmos migrar você de volta). Caso você nunca tenha migrado antes, é um processo automatizado que move suas imagens do sistema de arquivos para o novo host. Nenhuma mudança é necessária em sua parte, e o tempo de inatividade é limitado ao tempo necessário para copiar suas imagens (geralmente menos de 15 minutos ou mais por 3GB).
[*] Defina seu perfil de configuração para inicializar o kernel 2.4.26-linode29-1um
[*] Tente quebrar as coisas[/lista]
Se as coisas correrem bem por alguns dias, vou considerar estável e abrir o servidor para o público. Depois de mais algumas semanas, poderemos mover os outros hosts para este kernel.
Em segundo lugar, isto ajudará a testar o 2.6.7-rc1 no host, uma atualização do atual kernel 2.6.4.
Em terceiro lugar, gostaria também que alguns de vocês testassem o kernel 2.4.26-linode29-1um, para garantir que ele ainda funcione corretamente em hosts sem os patches sysemu. Por favor, me informem sobre sua experiência com este kernel. Em hosts não-sysemu habilitados, ele deve ter o mesmo desempenho que os kernels de linode anteriores.
Avise-me se você estiver interessado...
Obrigado!
-Chris
Comentários (17)
Three updates in one test? You’ve got ball-balls Chris!
😀
— James
I’m interested….let do it!
[quote:0999715663=”mcowger”]I’m interested….let do it![/quote]
Great. I haven’t patched a 2.6-um kernel with the sysemu patches yet, so for now go with the 2.4.26-linode29-1um kernel. I’ll update this thread when the 2.6 version is out.
Thanks!
-Chris
I’m game. What do I need to do?
Terry
[quote:31f75d1a84=”terryr”]I’m game. What do I need to do?[/quote]
Login, shutdown, and press the migrate button. After the migration, reboot.
BTW, 5 users have moved over to host25 and so far so good.
-Chris
Done! Are you looking for any specific feedback?
[quote:5c2da2598a=”terryr”]Done! Are you looking for any specific feedback?[/quote]
I pretty much know there’s a performance improvement already, but hearing about that would be nice. It might be kind of difficult to pin down, unless you run specific tests and compare them against the linode28 kernel. Secondly, I wanted to generate some load on the host kernel, and the linode29 kernel, just to make sure the stability is still there.
Thanks!
-Chris
I loaded a fresh Fedora Core 1 distro. Noticed immediately how much faster it is. Ran locate -u which was noticeably faster. Ran top and saw something strange. About every two seconds, there’s a cycle. See pics below. irq goes up to 0.9% and softirq goes up to 49.5% and iowait is 49.5%, then it all drops to 0 for 2 seconds and goes back up again for two seconds.
[img]http://futurecourse.com/files/no_softirq.gif[/img]
[img]http://futurecourse.com/files/softirq.gif[/img]
I don’t recall this happening when I looked at top on the old host. Or did I just miss it?
Terry
I am seeing stragne problems with mysql that I did not see before moving over. Whenever, I try to connect I get this message:
ERROR 2002: Can’t connect to local MySQL server through socket ‘/var/run/mysqld/mysqld.sock’ (2)
This is because mysqld either keeps hanging or completely crashes.
It will run fine for a few hours and then just die. I can’t explain why.
I will keep everyone posted.
John
[quote:04e5122a27=”jftuga”]I am seeing stragne problems with mysql that I did not see before moving over. Whenever, I try to connect I get this message:
ERROR 2002: Can’t connect to local MySQL server through socket ‘/var/run/mysqld/mysqld.sock’ (2)
This is because mysqld either keeps hanging or completely crashes.
It will run fine for a few hours and then just die. I can’t explain why.[/quote]
I’ve noticed your Linode using a lot of swap, so perhaps you’re running out of memory and the OOM (Out Of Memory) killer is kicking in…
-Chris
[quote:2ab259ee1d=”terryr”]I don’t recall this happening when I looked at top on the old host. Or did I just miss it? [/quote]
I’ll give this a shot, too, but.. would you mind rebooting into the linode28 kernel and seeing if you can reproduce this?
I somehow doubt the SYSEMU patch would be the cause of this, or the mysql problem…
-Chris
I have modified the mysql server for a small memory footprint using the my-small.cnf that comes with the src distro.
I will let you kno if this helps.
Also, I am using a lot of swap, and am considering upgrading to a 96 or 128 when they become available.
-John
[quote:befbb85d95=”caker”]I’ll give this a shot, too, but.. would you mind rebooting into the linode28 kernel and seeing if you can reproduce this? [/quote]
Did that yesterday with no change, but when I checked this morning, I’m at 0.1% for irq and softirq and it cycles with iowait at 0.2%. The high initial numbers didn’t seem to affect performance at all.
—
Terry
where is the migrate button? I shutodown and clicked around but I never found it.
[quote:f84ba42be4=”bakins”]where is the migrate button? I shutodown and clicked around but I never found it.[/quote]
This is something I have to set up for you first (which I just did). Login and you should see it.
Testing has gone very well. In fact, the machine is “live”, 2.6.7-rc1 is performing great (on the host), and the linode29 kernel works perfectly on SYSEMU and non-SYSEMU patched hosts.
I consider this test done, but go ahead and make the move — let me know what you think.
-Chris
I was out of town for a week.
I’ve now migrated and am testing. Everything seems to work. I’m testing out plone. I’ll do some tests and get back.
interesting… is this similar to the skas patch?