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c3a276111e
In these rules, each rule with the same (target type, target class, filename) values is (in practice) always mapped to the same result type. Therefore, it is much more efficient to group the rules by (ttype, tclass, filename). Thus, this patch drops the stype field from the key and changes the datum to be a linked list of one or more structures that contain a result type and an ebitmap of source types that map the given target to the given result type under the given filename. The size of the hash table is also incremented to 2048 to be more optimal for Fedora policy (which currently has ~2500 unique (ttype, tclass, filename) tuples, regardless of whether the 'unconfined' module is enabled). Not only does this dramtically reduce memory usage when the policy contains a lot of unconfined domains (ergo a lot of filename based transitions), but it also slightly reduces memory usage of strongly confined policies (modeled on Fedora policy with 'unconfined' module disabled) and significantly reduces lookup times of these rules on Fedora (roughly matches the performance of the rhashtable conversion patch [1] posted recently to selinux@vger.kernel.org). An obvious next step is to change binary policy format to match this layout, so that disk space is also saved. However, since that requires more work (including matching userspace changes) and this patch is already beneficial on its own, I'm posting it separately. Performance/memory usage comparison: Kernel | Policy load | Policy load | Mem usage | Mem usage | openbench | | (-unconfined) | | (-unconfined) | (createfiles) -----------------|-------------|---------------|-----------|---------------|-------------- reference | 1,30s | 0,91s | 90MB | 77MB | 55 us/file rhashtable patch | 0.98s | 0,85s | 85MB | 75MB | 38 us/file this patch | 0,95s | 0,87s | 75MB | 75MB | 40 us/file (Memory usage is measured after boot. With SELinux disabled the memory usage was ~60MB on the same system.) [1] https://lore.kernel.org/selinux/20200116213937.77795-1-dev@lynxeye.de/T/ Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com> |
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| 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.