Sono alla ricerca di alcuni utenti di Linode 64 attualmente su host nel datacenter di Fremont (da host9 in su) per aiutare a testare una nuova patch per le prestazioni dell'host e dell'UML.
UML funziona utilizzando ptrace, una funzione di Linux per intercettare le chiamate di sistema effettuate dalle applicazioni. Quando l'UML effettua una chiamata di sistema, l'host intercetta la chiamata, esegue il lavoro all'interno dell'UML e nullifica la chiamata di sistema sull'host convertendo la chiamata di sistema in "getpid" sull'host. Il problema di questa operazione è che genera due cambi di contesto sull'host.
Con le patch [url=http://perso.wanadoo.fr/laurent.vivier/UML/
]sysemu patch[/url] sull'host e in UML, non si preoccupa di eseguire "getpid", riducendo così il numero di cambi di contesto da 2 a 1.
[b]Parametri di riferimento[/b]
Ecco alcuni benchmark del "mondo reale" utilizzando lo script run-all-tests di Mysql:
http://www.theshore.net/~caker/uml/sysemu-benchmarks.txt
In breve, i test sono stati eseguiti il [b]33% più velocemente[/b] rispetto a quelli eseguiti senza le patch di sysemu.
[b]Dettagli[/b]
[Vi migreremo su host25, mantenendo il vostro slot sull'host precedente riservato (nel caso in cui dovessimo migrarvi di nuovo). Nel caso in cui non abbiate mai effettuato una migrazione, si tratta di un processo automatico che sposta le immagini del vostro filesystem sul nuovo host. Non sono necessarie modifiche da parte vostra e il tempo di inattività è limitato al tempo necessario per copiare le immagini (di solito meno di 15 minuti per 3GB).
[*] Impostare il profilo di configurazione per avviare il kernel 2.4.26-linode29-1um.
[*] Cercate di rompere le cose[/list]
Se le cose vanno bene per qualche giorno, lo considererò stabile e aprirò il server al pubblico. Dopo qualche altra settimana, potremo spostare gli altri host su questo kernel.
In secondo luogo, questo aiuterà a testare il kernel 2.6.7-rc1 sull'host, un aggiornamento rispetto all'attuale kernel 2.6.4.
In terzo luogo, vorrei che qualcuno di voi testasse il kernel 2.4.26-linode29-1um, per assicurarsi che funzioni ancora correttamente su host senza le patch di sysemu. Fatemi sapere la vostra esperienza con questo kernel. Su host non abilitati a sysemu, dovrebbe funzionare come i precedenti kernel linode.
Fatemi sapere se siete interessati...
Grazie!
-Chris
Commenti (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?