mainlining shenanigans
38935861d8
In isolate_migratepages_block, when cc->alloc_contig is true, we are
able to isolate compound pages. But nr_migratepages and nr_isolated did
not count compound pages correctly, causing us to isolate more pages
than we thought.
So count compound pages as the number of base pages they contain.
Otherwise, we might be trapped in too_many_isolated while loop, since
the actual isolated pages can go up to COMPACT_CLUSTER_MAX*512=16384,
where COMPACT_CLUSTER_MAX is 32, since we stop isolation after
cc->nr_migratepages reaches to COMPACT_CLUSTER_MAX.
In addition, after we fix the issue above, cc->nr_migratepages could
never be equal to COMPACT_CLUSTER_MAX if compound pages are isolated,
thus page isolation could not stop as we intended. Change the isolation
stop condition to '>='.
The issue can be triggered as follows:
In a system with 16GB memory and an 8GB CMA region reserved by
hugetlb_cma, if we first allocate 10GB THPs and mlock them (so some THPs
are allocated in the CMA region and mlocked), reserving 6 1GB hugetlb
pages via /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages will
get stuck (looping in too_many_isolated function) until we kill either
task. With the patch applied, oom will kill the application with 10GB
THPs and let hugetlb page reservation finish.
[ziy@nvidia.com: v3]
Link: https://lkml.kernel.org/r/20201030183809.3616803-1-zi.yan@sent.com
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.