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Currently, slab_sysfs_init() is an __initcall aka device_initcall. It is rather time-consuming; on my board it takes around 11ms. That's about 1% of the time budget I have from U-Boot letting go and until linux must assume responsibility of keeping the external watchdog happy. There's no particular reason this would need to run at device_initcall time, so instead make it a late_initcall to allow vital functionality to get started a bit sooner. This actually ends up winning more than just those 11ms, because the slab caches that get created during other device_initcalls (and before my watchdog device gets probed) now don't end up doing the somewhat expensive sysfs_slab_add() themselves. Some example lines (with initcall_debug set) before/after: initcall ext4_init_fs+0x0/0x1ac returned 0 after 1386 usecs initcall journal_init+0x0/0x138 returned 0 after 517 usecs initcall init_fat_fs+0x0/0x68 returned 0 after 294 usecs initcall ext4_init_fs+0x0/0x1ac returned 0 after 240 usecs initcall journal_init+0x0/0x138 returned 0 after 32 usecs initcall init_fat_fs+0x0/0x68 returned 0 after 18 usecs Altogether, this means I now get to petting the watchdog around 17ms sooner. [Of course, the time the other initcalls save is instead spent in slab_sysfs_init(), which goes from 11ms to 16ms, so there's no overall change in boot time.] Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> |
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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.