https://github.com/torvalds/linux
Revision 944dea41bf4dff0cfc4ce985884c6b2c8fa6b54b authored by Mauro Andreolini on 06 September 2015, 14:09:05 UTC, committed by Heather on 29 April 2016, 12:25:02 UTC
A set of processes may happen to perform interleaved reads, i.e.,requests whose union would give rise to a sequential read pattern. There are two typical cases: in the first case, processes read fixed-size chunks of data at a fixed distance from each other, while in the second case processes may read variable-size chunks at variable distances. The latter case occurs for example with QEMU, which splits the I/O generated by the guest into multiple chunks, and lets these chunks be served by a pool of cooperating processes, iteratively assigning the next chunk of I/O to the first available process. CFQ uses actual queue merging for the first type of rocesses, whereas it uses preemption to get a sequential read pattern out of the read requests performed by the second type of processes. In the end it uses two different mechanisms to achieve the same goal: boosting the throughput with interleaved I/O. This patch introduces Early Queue Merge (EQM), a unified mechanism to get a sequential read pattern with both types of processes. The main idea is checking newly arrived requests against the next request of the active queue both in case of actual request insert and in case of request merge. By doing so, both the types of processes can be handled by just merging their queues. EQM is then simpler and more compact than the pair of mechanisms used in CFQ. Finally, EQM also preserves the typical low-latency properties of BFQ, by properly restoring the weight-raising state of a queue when it gets back to a non-merged state. Signed-off-by: Mauro Andreolini <mauro.andreolini@unimore.it> Signed-off-by: Arianna Avanzini <avanzini@google.com> Signed-off-by: Paolo Valente <paolo.valente@unimore.it> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
1 parent 035b89b
Tip revision: 944dea41bf4dff0cfc4ce985884c6b2c8fa6b54b authored by Mauro Andreolini on 06 September 2015, 14:09:05 UTC
block, bfq: add Early Queue Merge (EQM) to BFQ-v7r11 for 4.4.0
block, bfq: add Early Queue Merge (EQM) to BFQ-v7r11 for 4.4.0
Tip revision: 944dea4
File | Mode | Size |
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Documentation | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.get_maintainer.ignore | -rw-r--r-- | 31 bytes |
.gitignore | -rw-r--r-- | 1.2 KB |
.mailmap | -rw-r--r-- | 5.5 KB |
COPYING | -rw-r--r-- | 18.3 KB |
CREDITS | -rw-r--r-- | 95.4 KB |
Kbuild | -rw-r--r-- | 2.6 KB |
Kconfig | -rw-r--r-- | 252 bytes |
MAINTAINERS | -rw-r--r-- | 344.2 KB |
Makefile | -rw-r--r-- | 55.0 KB |
README | -rw-r--r-- | 18.1 KB |
REPORTING-BUGS | -rw-r--r-- | 7.3 KB |
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