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Send WRs can be signalled or unsignalled. A signalled Send WR always has a matching Send completion, while a unsignalled Send has a completion only if the Send WR fails. xprtrdma has a Send account mechanism that is designed to reduce the number of signalled Send WRs. This in turn mitigates the interrupt rate of the underlying device. RDMA consumers can't leave all Sends unsignaled, however, because providers rely on Send completions to maintain their Send Queue head and tail pointers. xprtrdma counts the number of unsignaled Send WRs that have been posted to ensure that Sends are signalled often enough to prevent the Send Queue from wrapping. This mechanism neglected to account for FastReg WRs, which are posted on the Send Queue but never signalled. As a result, the Send Queue wrapped on occasion, resulting in duplication completions of FastReg and LocalInv WRs. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
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.