linux-kernel - Re: [PATCH next 0/2] THP COW support for private executable file mmap

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Message-ID: <5088b710-cfc5-417e-b629-c01d1eccb9b1@kernel.org>
Date: Mon, 15 Dec 2025 15:26:25 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Matthew Wilcox <willy@...radead.org>,
 Zhang Qilong <zhangqilong3@...wei.com>
Cc: akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com, corbet@....net,
 ziy@...dia.com, baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.com,
 npache@...hat.com, ryan.roberts@....com, dev.jain@....com,
 baohua@...nel.org, lance.yang@...ux.dev, vbabka@...e.cz, rppt@...nel.org,
 surenb@...gle.com, mhocko@...e.com, wangkefeng.wang@...wei.com,
 sunnanyong@...wei.com, linux-mm@...ck.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH next 0/2] THP COW support for private executable file mmap

On 12/15/25 15:00, Matthew Wilcox wrote:
> On Mon, Dec 15, 2025 at 08:34:05PM +0800, Zhang Qilong wrote:
>> This patch series implementate THP COW for private executable file
>> mmap. It's major designed to increase the iTLB cache hit rate for
>> hot patching application, and we add a new sysfs knob to disable or
>> enable it.
> 
> You're going to have to provide data to get this patch in.  We've
> deliberately not done this in the past due to memory consumption overhead.
> So you need to prove that's now the wrong decision to make.
> 
> Microbenchmarks would be a bare minimum, but what are really needed are
> numbers from actual workloads.

In addition, the sysfs toggle is rather horrible. It's rather clear that 
this is not a system-wide setting to be made, as you likely only want 
that behavior (if at all ...) for a handful of special processes I assume?

-- 
Cheers

David