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The refill operation of the xattr cache does not know the reply size in advance, so it makes a guess based on the maxeasize value returned by the MDS. In practice, it allocates 16 KiB for the common case and 4 MiB for the large xattr case. However, a typical reply is just a few hundred bytes. If we follow the conservative approach, we can prepare a single memory page for the reply. It is large enough for any reasonable xattr set and, at the same time, it does not require multiple page memory reclaim, which can be costly. If, for a specific file, the reply is larger than a single page, the client is prepared to handle that and will fall back to non-cached xattr code. Indeed, if this happens often and xattrs are often used to store large values, it makes sense to disable the xattr cache at all since it wasn't designed for such [mis]use. Signed-off-by: Andrew Perepechko <c17827@cray.com> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9417 Reviewed-on: https://review.whamcloud.com/26887 Reviewed-by: Fan Yong <fan.yong@intel.com> Reviewed-by: Ben Evans <bevans@cray.com> Reviewed-by: Oleg Drokin <oleg.drokin@intel.com> Signed-off-by: James Simmons <jsimmons@infradead.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.