RFR(XS): 8193521: glibc wastes memory with default configuration
adinn at redhat.com
Fri Dec 15 11:38:19 UTC 2017
On 15/12/17 10:39, Doerr, Martin wrote:
> The VM typically starts more than 20 threads even when only using
> java -version so we mmap several useless GB.
Also, I forgot to mention that it is not mmap calls per se that we need
to worry about but actual /physical commit/ of pages in the mmapped
region. We are not short of mappable address space and we don't incur
any significant cost by mapping the virtual address space we currently use.
I have no doubt your trace is showing a vmem page reservation rather
than a corresponding physical page commit. If the TLS regions mmapped in
your trace were really occupying several GBs of physical pages we would
already have done something about it.
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