Control: forwarded -1 https://lore.kernel.org/stable/[email protected]
Hi stable maintainers, Brian Maly reported in Debian (bugreport https://bugs.debian.org/1143545) when updating from the 6.1.y series to the 6.12.y series and noticed it is caused by 6.12.y missing the commit 1bc542c6a0d1 ("mm/vmscan: wake up flushers conditionally to avoid cgroup OOM"): On Mon, Aug 03, 2026 at 09:52:09PM -0400, Brian Maly wrote: > Package: kernel > Version: 6.12.94-1 > > > After upgrading from 6.1 series kernel to 6.12.x series kernel, a > performance regression was encountered. > > The customer is experiencing: > > ~2x slower execution times for write-heavy workloads under tight memory > cgroup limits (~256Mi) > > Significant latency spikes (median 14s vs 7.1s on kernel 6.1; max 23.5s vs > 7.6s) > > Occasional premature OOM conditions > > > Root Cause (Identified by Customer) > > The issue is an upstream Linux kernel MGLRU regression: > > Regression commit: 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging > cycle") ??? removed waking flusher threads during MGLRU reclaim, causing dirty > page accumulation and reclaim stalls under cgroup memory pressure. > > Fix commit: 1bc542c6a0d1 ("mm/vmscan: wake up flushers conditionally to > avoid cgroup OOM") ??? available in mainline ~6.13/6.14 but not backported to > the 6.12.x stable series (no Cc: stable tag). Ubuntu had to manually SRU it. > > Validation: Disabling MGLRU (/sys/kernel/mm/lru_gen/enabled=0) on kernel > 6.12 nodes restores near-6.1 performance and eliminates the latency tail, > confirming the MGLRU reclaim path as the cause. > > > Please include the fix commit in the 6.12 series kernel. Can you thus please backport/pick 1bc542c6a0d1 ("mm/vmscan: wake up flushers conditionally to avoid cgroup OOM") for 6.12.y? Regards, Salvatore
