https://github.com/torvalds/linux
Revision a8de6639169b90e3dc4f27e752a3c5abac5e90da authored by Alexey Dobriyan on 07 May 2020, 20:07:04 UTC, committed by Jens Axboe on 09 May 2020, 22:07:58 UTC
Pre-incrementing ->cq_head can't be done in memory because OOB value
can be observed by another context.
This devalues space savings compared to original code :-\
$ ./scripts/bloat-o-meter ../vmlinux-000 ../obj/vmlinux
add/remove: 0/0 grow/shrink: 0/4 up/down: 0/-32 (-32)
Function old new delta
nvme_poll_irqdisable 464 456 -8
nvme_poll 455 447 -8
nvme_irq 388 380 -8
nvme_dev_disable 955 947 -8
But the code is minimal now: one read for head, one read for q_depth,
one increment, one comparison, single instruction phase bit update and
one write for new head.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: John Garry <john.garry@huawei.com>
Tested-by: John Garry <john.garry@huawei.com>
Fixes: e2a366a4b0feaeb ("nvme-pci: slimmer CQ head update")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 parent 6bd87ee
Tip revision: a8de6639169b90e3dc4f27e752a3c5abac5e90da authored by Alexey Dobriyan on 07 May 2020, 20:07:04 UTC
nvme-pci: fix "slimmer CQ head update"
nvme-pci: fix "slimmer CQ head update"
Tip revision: a8de663
| File | Mode | Size |
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | -rw-r--r-- | 15.5 KB |
| .cocciconfig | -rw-r--r-- | 59 bytes |
| .get_maintainer.ignore | -rw-r--r-- | 71 bytes |
| .gitattributes | -rw-r--r-- | 62 bytes |
| .gitignore | -rw-r--r-- | 1.7 KB |
| .mailmap | -rw-r--r-- | 15.1 KB |
| COPYING | -rw-r--r-- | 496 bytes |
| CREDITS | -rw-r--r-- | 97.4 KB |
| Kbuild | -rw-r--r-- | 1.3 KB |
| Kconfig | -rw-r--r-- | 595 bytes |
| MAINTAINERS | -rw-r--r-- | 539.1 KB |
| Makefile | -rw-r--r-- | 59.9 KB |
| README | -rw-r--r-- | 727 bytes |
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