hg: hsx/hotspot-gc/hotspot: 2 new changesets

Florian Weimer fweimer at bfk.de
Wed Aug 10 08:09:28 PDT 2011

* Ramki Ramakrishna:

> I couldn't tell from the subsequent discussion, if this is by design
> in Linux or an inadvertent bug (at least the Linux man page is mum on
> the swap reservation semantics of MADV_DONTNEED; Solaris does not lose
> page reservations on an madvise; so we'll have to defer to people
> familiar with the Linux kernel to interpret intentions and semantics
> here).

In Linux, Hotspot should not use MAP_NORESERVE, but map with PROT_NONE
initially and upgrade that to PROT_READ | PROT_WRITE (using mprotect) as
heap usage grows.  Then MADV_DONTNEED will do the right thing with
regards to swap reservation.  IIRC, MAP_NORESERVE results in a SIGSEGV
signal which Hotspot cannot handle properly at the moment.

Florian Weimer                <fweimer at bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstraße 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99

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