7f5d3f2721
Timestamps in pktgen are currently retrieved using the deprecated do_gettimeofday() function that wraps its signed 32-bit seconds in 2038 (on 32-bit architectures) and requires a division operation to calculate microseconds. The pktgen header is also defined with the same limitations, hardcoding to a 32-bit seconds field that can be interpreted as unsigned to produce times that only wrap in 2106. Whatever code reads the timestamps should be aware of that problem in general, but probably doesn't care too much as we are mostly interested in the time passing between packets, and that is correctly represented. Using 64-bit nanoseconds would be cheaper and good for 584 years. Using monotonic times would also make this unambiguous by avoiding the overflow, but would make it harder to correlate to the times with those on remote machines. Either approach would require adding a new runtime flag and implementing the same thing on the remote side, which we probably don't want to do unless someone sees it as a real problem. Also, this should be coordinated with other pktgen implementations and might need a new magic number. For the moment, I'm documenting the overflow in the source code, and changing the implementation over to an open-coded ktime_get_real_ts64() plus division, so we don't have to look at it again while scanning for deprecated time interfaces. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| README | ||
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.