mirror of
https://github.com/torvalds/linux.git
synced 2026-07-31 19:47:08 +02:00
Linux kernel source tree
d1ba22ab2b
[BUG] There has an issue of io delayed dispatch caused by io splitting. Consider the following scenario: 1) If we set a BPS limit of 1MB/s and restrict the maximum IO size per dispatch to 4KB, submitting -two- 1MB IO requests results in completion times of 1s and 2s, which is expected. 2) However, if we additionally set an IOPS limit of 1,000,000/s with the same BPS limit of 1MB/s, submitting -two- 1MB IO requests again results in both completing in 2s, even though the IOPS constraint is being met. [CAUSE] This issue arises because BPS and IOPS currently share the same queue in the blkthrotl mechanism: 1) This issue does not occur when only BPS is limited because the split IOs return false in blk_should_throtl() and do not go through to throtl again. 2) For split IOs, even if they have been tagged with BIO_BPS_THROTTLED, they still get queued alternately in the same list due to continuous splitting and reordering. As a result, the two IO requests are both completed at the 2-second mark, causing an unintended delay. 3) It is not difficult to imagine that in this scenario, if N 1MB IOs are issued at once, all IOs will eventually complete together in N seconds. [FIX] With the queue separation introduced in the previous patches, we now have separate BPS and IOPS queues. For IOs that have already passed the BPS limitation, they do not need to re-enter the BPS queue and can directly placed to the IOPS queue. Since we have split the queues, when the IOPS queue is previously empty and a new bio is added to the first qnode->bios_iops list in the service_queue, we also need to update the disptime. This patch introduces "THROTL_TG_IOPS_WAS_EMPTY" flag to mark it. Signed-off-by: Zizhi Wo <wozizhi@huawei.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Zizhi Wo <wozizhi@huaweicloud.com> Link: https://lore.kernel.org/r/20250506020935.655574-8-wozizhi@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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 reStructuredText 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.