mainlining shenanigans
03fe78cc29
We have been hitting some early ENOSPC issues in production with more recent kernels, and I tracked it down to us simply not flushing delalloc as aggressively as we should be. With tracing I was seeing us failing all tickets with all of the block rsvs at or around 0, with very little pinned space, but still around 120MiB of outstanding bytes_may_used. Upon further investigation I saw that we were flushing around 14 pages per shrink call for delalloc, despite having around 2GiB of delalloc outstanding. Consider the example of a 8 way machine, all CPUs trying to create a file in parallel, which at the time of this commit requires 5 items to do. Assuming a 16k leaf size, we have 10MiB of total metadata reclaim size waiting on reservations. Now assume we have 128MiB of delalloc outstanding. With our current math we would set items to 20, and then set to_reclaim to 20 * 256k, or 5MiB. Assuming that we went through this loop all 3 times, for both FLUSH_DELALLOC and FLUSH_DELALLOC_WAIT, and then did the full loop twice, we'd only flush 60MiB of the 128MiB delalloc space. This could leave a fair bit of delalloc reservations still hanging around by the time we go to ENOSPC out all the remaining tickets. Fix this two ways. First, change the calculations to be a fraction of the total delalloc bytes on the system. Prior to this change we were calculating based on dirty inodes so our math made more sense, now it's just completely unrelated to what we're actually doing. Second add a FLUSH_DELALLOC_FULL state, that we hold off until we've gone through the flush states at least once. This will empty the system of all delalloc so we're sure to be truly out of space when we start failing tickets. I'm tagging stable 5.10 and forward, because this is where we started using the page stuff heavily again. This affects earlier kernel versions as well, but would be a pain to backport to them as the flushing mechanisms aren't the same. CC: stable@vger.kernel.org # 5.10+ Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
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| usr | ||
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| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| 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.