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The account_system_time() function is called with a cputime that occurred while running in the kernel. The function detects which context the CPU is currently running in and accounts the time to the correct bucket. This forces the arch code to account the cputime for hardirq and softirq immediately. Such accounting function can be costly and perform unwelcome divisions and multiplications, among others. The arch code can delay the accounting for system time. For s390 the accounting is done once per timer tick and for each task switch. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> [ Rebase against latest linus tree and move account_system_index_scaled(). ] Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Wanpeng Li <wanpeng.li@hotmail.com> Link: http://lkml.kernel.org/r/1483636310-6557-10-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| certs | ||
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| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
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| ipc | ||
| kernel | ||
| lib | ||
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| net | ||
| samples | ||
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| tools | ||
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| virt | ||
| .cocciconfig | ||
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| Kconfig | ||
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| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.