Two Very Exciting Memory Management Optimizations Going Into Linux 7.3 - Phoronix

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Two Very Exciting Memory Management Optimizations Going Into Linux 7.3

Written by Michael Larabel in Linux Kernel on 19 August 2026 at 04:31 PM EDT. 3 Comments

Andrew Morton on Tuesday sent out all of the memory management "MM" updates for the Linux 7.3 merge window. The MM pull was particularly heavy as he noted 1,250 "added-to-MM" emails were sent out this cycle compared to 920 the prior cycle. With a lot of patch churn, he also turned to Google's Gemini AI for writing his patch summaries. In going through the very verbose AI-generated summary, there are two patch series that get me excited on the performance front with Linux 7.3.

First up there is a patch series for reducing locking contention in zs_free(), which is part of the zsmalloc memory allocator on Linux and used by Zswap and zRAM for releasing compressed RAM pages. Locking contention within zs_free() can be significant in the unmapping path when systems are under memory pressure either on Google Android devices or on servers with Zswap-heavy workloads. Given the increase in Zswap/zRAM usage with today's memory prices especially for large servers, this locking contention optimization can be very helpful.

In benchmarking the performance impact of this reduced locking contention within zsmalloc, both a 20-core Intel system and small Raspberry Pi 4B benefited nicely when measuring the time for each process independently mapping 256MB, writing data, madvise'ing page-out to swap out via zRAM, and then concurrent unmapping. Wenchao Hao of Xiaomi found that the Raspberry Pi sped up by as much as 1.83x in this operation while the Intel system was up to 1.4x.

Separately, but also part of the MM pull request, are performance optimizations for rmap_walk_ksm(). The rmap_walk_ksm memory management function is for carrying out a reverse map walk for pages managed via Kernel Samepage Merging (KSM). ZTE engineers discovered a "severe" performance problem with KSM reverse-mapping where applications can freeze for hundreds of milliseconds under memory pressure. The problem was most pronounced when a lot of unrelated VMAs share a single anon_vma.

The problem is so severe that lock hold times dropped from more than 500ms to less than 2ms! In the worst case scenario going from 705ms down to a 1.44ms average or 1.67ms max.

Xu Xin of ZTE elaborated on the performance impact and some real-world examples in the prior patch series:<br>"Two key highlights:

1. Lock hold time drops from >500ms to MM updates for Linux 7.3.

These are far from the only performance optimizations coming, with several others noted in other Phoronix articles recently. Linux 7.3 kernel benchmarking will be firing up soon on Phoronix once the merge window settles down.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.

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