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On relatively slow development platforms and software models, the inefficiency of our TLB sync loop tends not to show up - for instance on a Juno r1 board I typically see the TLBI has completed of its own accord by the time we get to the sync, such that the latter finishes instantly. However, on larger systems doing real I/O, it's less realistic for the TLBs to go idle immediately, and at that point falling into the 1MHz polling loop turns out to throw away performance drastically. Let's strike a balance by polling more than once between pauses, such that we have much more chance of catching normal operations completing before committing to the fixed delay, but also backing off exponentially, since if a sync really hasn't completed within one or two "reasonable time" periods, it becomes increasingly unlikely that it ever will. Reviewed-by: Jordan Crouse <jcrouse@codeaurora.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
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.