499197dc16
Our goal is to remove struct_mutex and replace it with fine grained locking. One of the thorny issues is our eviction logic for reclaiming space for an execbuffer (or GTT mmaping, among a few other examples). While eviction itself is easy to move under a per-VM mutex, performing the activity tracking is less agreeable. One solution is not to do any MRU tracking and do a simple coarse evaluation during eviction of active/inactive, with a loose temporal ordering of last insertion/evaluation. That keeps all the locking constrained to when we are manipulating the VM itself, neatly avoiding the tricky handling of possible recursive locking during execbuf and elsewhere. Note that discarding the MRU (currently implemented as a pair of lists, to avoid scanning the active list for a NONBLOCKING search) is unlikely to impact upon our efficiency to reclaim VM space (where we think a LRU model is best) as our current strategy is to use random idle replacement first before doing a search, and over time the use of softpinned 48b per-ppGTT is growing (thereby eliminating any need to perform any eviction searches, in theory at least) with the remaining users being found on much older devices (gen2-gen6). v2: Changelog and commentary rewritten to elaborate on the duality of a single list being both an inactive and active list. v3: Consolidate bool parameters into a single set of flags; don't comment on the duality of a single variable being a multiplicity of bits. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190128102356.15037-1-chris@chris-wilson.co.uk
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.