b9ff43dd27
Reading 100KB chunks from a big file (eg dd bs=100K) leads to poor readahead behaviour. Studying the traces in detail, I noticed two problems. The first is that we were setting the readahead flag on the folio which contains the last byte read from the block. This is wrong because we will trigger readahead at the end of the read without waiting to see if a subsequent read is going to use the pages we just read. Instead, we need to set the readahead flag on the first folio _after_ the one which contains the last byte that we're reading. The second is that we were looking for the index of the folio with the readahead flag set to exactly match the start + size - async_size. If we've rounded this, either down (as previously) or up (as now), we'll think we hit a folio marked as readahead by a different read, and try to read the wrong pages. So round the expected index to the order of the folio we hit. Reported-by: Guo Xuenan <guoxuenan@huawei.com> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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 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.