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d4c5e960bf
Linus observed that an allmodconfig build which does a lot of stat(2) calls that ext4_getattr() was a noticeable (1%) amount of CPU time, due to the cache line for i_extra_isize getting pulled in. Since the normal stat system call doesn't return btime, it's a complete waste. So only calculate btime when it is explicitly requested. [ Fixed to check against request_mask instead of query_flags. ] Link: https://lore.kernel.org/r/CAHk-=wivmk_j6KbTX+Er64mLrG8abXZo0M10PNdAnHc8fWXfsQ@mail.gmail.com Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Andreas Dilger <adilger@dilger.ca> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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.