** Changed in: linux (Ubuntu Artful)
Status: Fix Committed => Fix Released
** Changed in: intel
Status: New => Fix Released
** Information type changed from Private to Public
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https://bugs.launchpad.net/bugs/1646723
Title:
[Feature] Swap optimizations to enable fast block devices to be used
as secondary memory
Status in intel:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Artful:
Fix Released
Bug description:
Improved swap performance benefits the new generation of Solid state Block
devices. Their latencies are getting down to sub 100 usec, which is within an
order of magnitude of DRAM, and their performance is orders of magnitude higher
than the single- spindle rotational media we've swapped to historically.
This could benefit many usage scenarios. For example cloud providers who
overcommit their memory (as VM don't use all the memory provisioned).
Having a fast swap will allow them to be more aggressive in memory overcommit
and fit more VMs to a platform.
In our testing, the median latency that the kernel adds to a page fault is 15
usec, which comes quite close
to the amount that will be contributed by the underlying I/O devices.
The software latency comes mostly from contentions on the locks protecting
the radix tree of the swap cache and also the locks protecting the individual
swap devices. The lock contentions already consumed 35% of cpu cycles in our
test. In the very near future, software latency will become the bottleneck to
swap performance as block device I/O latency gets within the shouting distance
of DRAM speed.
upstream schedule:
kernel: 4.10
Patchset send to ML:
http://marc.info/?l=linux-mm&m=147925369906911&w=2
https://lwn.net/Articles/704478/
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