From: Andrew Morton <akpm@linux-foundation•org>
To: Usama Arif <usama.arif@linux•dev>
Cc: david@kernel•org, willy@infradead•org, ryan.roberts@arm•com,
linux-mm@kvack•org, r@hev•cc, jack@suse•cz,
Andrew Donnellan <andrew+kernel@donnellan•id.au>,
apopple@nvidia•com, baohua@kernel•org,
baolin.wang@linux•alibaba.com, brauner@kernel•org,
catalin.marinas@arm•com, dev.jain@arm•com, kees@kernel•org,
kevin.brodsky@arm•com, lance.yang@linux•dev,
Liam R.Howlett <liam@infradead•org>,
linux-arm-kernel@lists•infradead.org,
linux-fsdevel@vger•kernel.org, linux-kernel@vger•kernel.org,
ljs@kernel•org, mhocko@suse•com, npache@redhat•com,
pasha.tatashin@soleen•com, rmclure@linux•ibm.com,
rppt@kernel•org, surenb@google•com, vbabka@kernel•org,
Al Viro <viro@zeniv•linux.org.uk>,
wilts.infradead.org@hp2•hsd1.ca.comcast.net,
"linux-fsdevel@vger.kernel.l"@kernel.org, ziy@nvidia•com,
hannes@cmpxchg•org, kas@kernel•org, shakeel.butt@linux•dev,
kernel-team@meta•com
Subject: Re: [PATCH v6 0/2] mm: improve large folio readahead for exec memory
Date: Thu, 28 May 2026 13:27:28 -0700 [thread overview]
Message-ID: <20260528132728.c47a38e7506483d587f64eb7@linux-foundation.org> (raw)
In-Reply-To: <20260528165635.2068012-1-usama.arif@linux.dev>
On Thu, 28 May 2026 09:55:18 -0700 Usama Arif <usama.arif@linux•dev> wrote:
> Two checks in do_sync_mmap_readahead() limit large-folio readahead:
>
> 1. The mmap_miss heuristic is meant to throttle wasteful speculative
> readahead. It is currently also applied to the VM_EXEC readahead
> path, which is targeted rather than speculative. Once mmap_miss exceeds
> MMAP_LOTSAMISS, exec readahead - including the large-folio
> order requested by exec_folio_order() - is disabled. On
> configurations where the mmap_miss decrement paths are not
> active (see patch 1) the counter only grows, so exec readahead
> is permanently disabled after the first 100 faults.
>
> 2. The force_thp_readahead path is gated only on
> HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER and always drives the
> readahead at HPAGE_PMD_ORDER. Configurations where
> HPAGE_PMD_ORDER exceeds MAX_PAGECACHE_ORDER never reach this
> path, even when the mapping itself supports usefully large
> folios well below the cap.
>
> Both issues are most visible on arm64 with a 64K base page size,
> where HPAGE_PMD_ORDER is 13 (512MB) -- above MAX_PAGECACHE_ORDER
> (11) -- and where fault_around_pages collapses to 1 disabling
> should_fault_around() (one of the two mmap_miss decrement sites).
> However the fixes are architecture-agnostic: patch 1 reflects the
> nature of VM_EXEC readahead regardless of base page size, and
> patch 2 generalises the gate so any mapping advertising a usefully
> large maximum folio order can benefit.
OK, thanks, it's getting late and [2/2] hasn't yet been reviewed. I'll
add it, just, because I'm a sucker for speedups.
next parent reply other threads:[~2026-05-28 21:34 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260528165635.2068012-1-usama.arif@linux.dev>
2026-05-28 20:27 ` Andrew Morton [this message]
[not found] ` <20260528165635.2068012-2-usama.arif@linux.dev>
2026-05-29 9:47 ` [PATCH v6 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Pedro Falcato
[not found] ` <20260528165635.2068012-3-usama.arif@linux.dev>
2026-05-29 10:01 ` [PATCH v6 2/2] mm: use mapping_max_folio_order() for force_thp_readahead order Pedro Falcato
2026-05-29 12:19 ` Usama Arif
2026-05-29 13:40 ` Pedro Falcato
2026-05-29 14:11 ` Usama Arif
2026-05-30 15:16 ` Jan Kara
2026-06-01 9:43 ` Usama Arif
2026-06-02 17:35 ` Pedro Falcato
2026-06-03 10:10 ` Usama Arif
2026-06-03 11:51 ` Pedro Falcato
2026-06-02 17:46 ` Pedro Falcato
2026-05-29 12:36 ` Usama Arif
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