Am Samstag, den 27.01.2007, 00:15 -0700 schrieb Bernard Johnson:
Nils Toedtmann wrote:
I guess they did not disappear but got hidden. AFAIK (correct me if i am wrong) recent xen versions have a hack to workaround TLS-libs silently, but there is still a performance penalty.
That was not my understanding, however you may be right. Can you point me to documentation as to what the workaround actually does? And what performance penalty we might be paying?
Am Sonntag, den 28.01.2007, 18:45 +0000 schrieb Karanbir Singh:
Do you have some numbers to elaborate on the point of performance loss ?
OK, i digged the MLs ...
If there are Xen-incompatible NPTL/TLS libs, then Xen3 does a "TLS emulation" which gives threaded apps a performance penalty, at least on i86_32 systems (i am not sure about i86_64):
http://wiki.xensource.com/xenwiki/XenFaq (item 4.1) http://wiki.xensource.com/xenwiki/XenSpecificGlibc http://lists.xensource.com/archives/cgi-bin/namazu.cgi?query=%22tls +emulation%22&submit=Search&idxname=xen-users
This mail
http://lists.xensource.com/archives/html/xen-users/2007-01/msg00913.html
from Xen developer Keir Fraser is 9 days old and references to Xen 3.0.4 (which unfortunatly _needs_ TLS in Dom0 for xen-libs):
"For now you can simply use the /lib/tls libraries — you’ll get a warning during boot and performance in domain0 will be reduced"
From the rumors i have read on the xen MLs, OpenLDAP and java suffer
from that problem heavily, but i did not find benchmarks comparing xen-compatible vs. xen-emulated TLS. Sorry, that is all i can tell on that topic, i'm just another admin reading MLs...
/nils.