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The existing "auto eq delay" mechanism was sometimes skipping over an EQ,
not ramping the coalescing down under light load fast enough, and in other
cases never kicked in as cpu sharing by multiple vectors didn't quite add
up right.
Tweak the interrupt mechanism such that:
- Add a flag to the EQ to force checking for colaescing values when being
serviced in the interrupt handler. The flag will be set by any CQ bound
to the EQ whenever the number of CQ elements process in a single scan
meets or exceeds the hardware queue notify level. E.g. there's a
significant number of completions happening.
- In the heartbeat work item that checks coalescing:
- Replace the structure that was counting the number of EQs that
interrupted on a single cpu with a new structure that looks at the EQ
to see whether EQ currently has a coalescing value (thus it should be
re-evaluate) or was marked by the new flag indicating heavy
completions.
- When a cpu, which may be servicing multiple vectors, had at least 1 EQ
that should be checked, a new coalescing delay is calculated based on
the number of interrupts that occurred on the cpu.
- The new coalescing value is then applied to the EQs that had
interrupted on the cpu.
Link: https://lore.kernel.org/r/20191018211832.7917-11-jsmart2021@gmail.com
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.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
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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.