Huan Yang
6b68b74a08
Currently, udmabuf handles folio by create an unpin list to record each folio obtained from the list and unpinning them when released. To maintain this, many struct have been established. However, maintain this requires a significant amount of memory and iter the list is a substantial overhead, which is not friendly to the CPU cache. When create, we arranged the folio array in the order of pin and set the offset according to pgcnt. So, if record each pinned folio when create, then can easy unpin it. Compare to use list to record it, an array also can do this. Hence, this patch setup a pinned_folios array(size is the pgcnt) to instead of udmabuf_folio struct, it record each folio which pinned when invoke memfd_pin_folios, then unpin folio by iter pinned_folios. Note that, since a folio may be pinned multiple times, each folio can be added to pinned_folios multiple times, depend on how many times the folio has been pinned when create. Compare to udmabuf_folio(24 byte size), a folio pointer is 8 byte, if no large folio - each folio is PAGE_SIZE - and need to unpin when release. So need to record each folio, by this patch, each folio can save 16 byte. But if large folio used, depend on the large folio's number, the pinned_folios array may take more memory, but it still can makes unpin access more cache-friendly. Signed-off-by: Huan Yang <link@vivo.com> Acked-by: Vivek Kasireddy <vivek.kasireddy@intel.com> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240918025238.2957823-7-link@vivo.com
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 reStructuredText 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.