Ticket #10600 (closed defect: fixed)
vbi_internal_alloc() should not call contig_alloc() for large allocations => Fixed in SVN
|Reported by:||blakej||Owned by:|
A user of VirtualBox 4.1.16, with Solaris s11u1_16 as the host, commented that he was seeing "virtualbox's guru-meditation-screen-of-death due to not being able to allocate and lock memory [...] even though plenty of memory is available." The relevant comment from his logfile was:
PGMR3PhysAllocateLargePage: allocating large pages takes too long
(last attempt 8462 ms; nr of timeouts 1); DISABLE
I asked him to look into what VirtualBox was doing when it generated that error message. He found that it was in the vbox driver, making a call from vbi_internal_alloc() -> contig_alloc() -> page_create_io() -> delay().
Further investigation showed that vbi_internal_alloc() was being called with a size of 2MB, an alignment of 2MB, a high-address limitation of 264 - 1 (i.e. no limitation), and a request for contiguity. In other words, it just wanted a single large page.
Looking at the VBox 4.1.16 source, vbi_internal_alloc() calls contig_alloc() to get this page. As it turns out, contig_alloc() is just about the slowest imaginable way to allocate a single large page -- it assumes that it needs to respect the rest of the ddi_dma_attr_t, and it doesn't assume that it's nicely page-aligned, so it may end up trawling through huge amounts of the system's memory trying to stitch together a valid region for the caller.
If you would like information on a better approach for doing this, please contact me directly -- my email is blake.a.jones at oracle.com. (I am the technical lead for the VM2 project in Solaris.) I expect that a different approach might go 100x faster.
- Summary changed from vbi_internal_alloc() should not call contig_alloc() to vbi_internal_alloc() should not call contig_alloc() for large allocations
- Summary changed from vbi_internal_alloc() should not call contig_alloc() for large allocations to vbi_internal_alloc() should not call contig_alloc() for large allocations => Fixed in SVN