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Date: Mon, 6 Apr 2026 12:16:01 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "JP Kobryn (Meta)" <jp.kobryn@linux.dev>
Cc: linux-mm@kvack.org, willy@infradead.org, hannes@cmpxchg.org,
 david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com,
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 kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev,
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 netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH v3] mm/vmpressure: skip socket pressure for costly order
 reclaim
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On Mon, 6 Apr 2026 12:07:57 -0700 "JP Kobryn (Meta)" <jp.kobryn@linux.dev> wrote:

> Let me know if this data helps, and if you'd like this added to the
> changelog.
> 
> On one affected host with impacted net throughput, the memory state at
> the time showed ~15GB available, zero cgroup pressure, and the following
> buddyinfo state:
> 
> Order FreePages
> 0:    133,970
> 1:    29,230
> 2:    17,351
> 3:    18,984
> 7+:   0
> 
> Using bpf, it was found that 94% of vmpressure calls on this host were
> from order-7 kswapd reclaim.
> 
> TCP minimum recv window is rcv_ssthresh:19712.
> 
> Before patch:
> 723 out of 3,843 (19%) TCP connections stuck at minimum recv window
> 
> After live-patching and ~30min elapsed:
> 0 out of 3,470 TCP connections stuck at minimum recv window

Well I'm impressed ;)

Yes please, it's a useful thing to include.  When people look at a
contribution, question #1 is "why should I spend time on this".  A
clear (and tasty) description of userspace benefit is the ideal way of
answering that.