G1 is bad for me

[Chi Ho Kwok]

Hi all,

A large part of our CPU load is caused by GC, so I'm always interested in
new techniques, but the last time I tried G1 (6u14?), the jvm rapidly
crashed after startup under load. Is the recommendation to switch to/wait
for JDK7 releases for G1, or is G1 on 6u18 (or later?) any good for
production usage? I'd assume there will be more updates for JDK6 as JDK7 got
extended to up to 10 milestones.

CMS with a 32G heap which changes rapidly (~10%/min replaced) is manageable,
but we're "losing" 20% capacity because the threshold has to be so low,
anything higher than 80% causes new gen promotions to fail during CMS and
the app to stop for half a minute. Processing capacity is also reduced by
half during a CMS run because the amount of threads has to be high (=6 at
the moment) to make it hurry up, or it'll mean either setting the threshold
even lower or risk promotion failures :(

Chi Ho Kwok

On Thu, Feb 18, 2010 at 6:37 PM, Y. Srinivas Ramakrishna <
Y.S.Ramakrishna at sun.com> wrote:

> Hi Andrei -- please use the latest hs17 JVM which you can get from JDK 7.
> There have been
> many improvements (and bug fixes) since the 6u18/hs16 that you are using
> below.
> Most importantly, please add -XX:-ReduceInitialCardMarks to work around a
> regression
> introduced in 6u18/hs16, as described in the 6u18 release notes.
> As re optimal settings (these may be quite different from shapes that
> helped with CMS
> for example), i'll let others w/more (tuning and other) experience w/G1
> comment.
>
> -- ramki
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