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LWN on Tiered-memory Systems and TCMalloc
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LWN ☛ Recent work in memory tiering
Tiered-memory systems are built with multiple types of memory, each of which has different performance characteristics. In addition to the usual DRAM, a tiered system might also provide faster high-bandwidth memory or slower CXL memory. On these systems, the placement of memory allocations has a significant effect on the performance that a workload will obtain. While work on tiered-memory improvements has been ongoing for years, it feels like the pace has slowed a bit recently. Even so, there are a few efforts underway, but they are facing questions about whether the tiering design makes sense.
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LWN ☛ Fixing the TCMalloc regression with RSEQ operations
The restartable sequences feature is one of the stranger corners of the kernel's user-space interface; it provides a way for user space to carry out simple lockless operations and be informed if it is preempted over the course of an operation (and must, thus, restart). Work merged in the 6.19 release to improve the performance of restartable sequences broke the TCMalloc allocator, which was relying on an undocumented (and unintended) kernel behavior. Now, Olivier Dion is proposing an addition to the restartable-sequences API that will bring TCMalloc back into the fold; it does not make the restartable-sequences API any less strange, though.