Public bug reported:
Linux has developed a reputation for sluggish performance under heavy
disk I/O, e.g. during system updates. This seems to be mostly due to its
inability to distinguish urgent tasks from I/O hogs, resulting in
preferential treatment of hogs (and thus sluggishness under load). This
applies even on very high-end computers.
On a server, this (probably) doesn't matter a great deal. On a desktop,
it matters a lot, because users will generally not tolerate
sluggishness, especially on computers that are supposed to be fast (as a
famous company from Redmond discovered when they released a shiny new OS
in 2007). Since Ubuntu is primarily a desktop distribution, and
currently the most popular, I think it would be a good idea to try and
solve this issue.
The only solution that I know to work reliably is to set vm.dirty_bytes
(and vm.dirty_background_bytes) to something relatively low. This forces
programs to make smaller and more frequent writes to the disk,
preventing processes from hogging huge amounts of I/O bandwidth. In my
experience, 4 MB (4194304 bytes) is a sane value; it increases
responsiveness under load (and even during desktop startup) greatly,
while only reducing throughput by a few MB/s on modern computers. Since
I care more about latency than throughput, I consider this a decent
tradeoff.
The only major issue I can see with this change is that it might
increase wear on SSDs; but I'm not sure how much, or if it's worth
making an exception for SSDs.
** Affects: linux-lts-backport-oneiric (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/908279
Title:
vm.dirty_bytes should be set to something sane
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