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, pfalcato@suse•de, 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>,
ziy@nvidia•com, hannes@cmpxchg•org, kas@kernel•org,
shakeel.butt@linux•dev, kernel-team@meta•com
Subject: Re: [PATCH v7 0/2] mm: improve large folio readahead for exec memory
Date: Mon, 1 Jun 2026 16:10:26 -0700 [thread overview]
Message-ID: <20260601161026.d5905786bbd3a26d62be88c3@linux-foundation.org> (raw)
In-Reply-To: <20260601102205.3985788-1-usama.arif@linux.dev>
On Mon, 1 Jun 2026 03:21:16 -0700 Usama Arif <usama.arif@linux•dev> wrote:
> Hopefully this is the last revision. The only change from the previous
> revision is that the logic for deciding THP order was simplified and
> the max is now capped to 2M. Thanks Pedro and Jan for the suggestion
> and the dicusssion!
>
> The benchmark results on Neoverse V2 (Grace), arm64 with 64K base pages,
> 512MB executable file on ext4, averaged over 3 runs:
>
> Phase | Baseline | Patched | Improvement
> -----------|--------------|--------------|------------------
> Cold fault | 83.4 ms | 41.3 ms | 50% faster
> Random | 76.0 ms | 58.3 ms | 23% faster
>
> The patches are on top of mm-unstable from 28 May
> (8a74e22643189e0ae339afc91110ddb4cab1941b) which include patch [1]
> that make mmap_miss accounting symmetric for VM_SEQ_READ which was pointed
> out by sashiko in the previous revision.
We lost the [0/N] cover letter. Please do retain (and maintain!) that
across revisions. I used the one from the v6 patchset.
> v6 -> v7: https://lore.kernel.org/all/20260528165635.2068012-1-usama.arif@linux.dev/
> - Simplify logic and just cap the max THP order to 2M (Pedro and Jan)
Here's how v7 altered mm.git:
mm/filemap.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
--- a/mm/filemap.c~b
+++ a/mm/filemap.c
@@ -3320,17 +3320,12 @@ static struct file *do_sync_mmap_readahe
/* Use the readahead code, even if readahead is disabled */
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && (vm_flags & VM_HUGEPAGE)) {
/*
- * Preserve PMD-sized readahead where it already fits in
- * the page cache. Otherwise cap the new fallback path at
- * 2MB: this is the common PMD-sized hugepage size, and it
- * avoids memory pressure from very large forced readahead
- * when mapping_max_folio_order() is high (for example,
- * 128MB with 64K base pages on arm64).
+ * Cap max THP order at 2MB: this is the common PMD-sized
+ * hugepage size, and it avoids memory pressure from very
+ * large forced readahead when mapping_max_folio_order() is
+ * high (for example, 128MB with 64K base pages on arm64).
*/
- if (HPAGE_PMD_ORDER <= MAX_PAGECACHE_ORDER) {
- force_thp_readahead = true;
- thp_order = HPAGE_PMD_ORDER;
- } else if (mapping_large_folio_support(mapping)) {
+ if (mapping_large_folio_support(mapping)) {
force_thp_readahead = true;
thp_order = min_t(unsigned int,
mapping_max_folio_order(mapping),
_
prev parent reply other threads:[~2026-06-01 23:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-01 10:21 [PATCH v7 0/2] mm: improve large folio readahead for exec memory Usama Arif
2026-06-01 10:21 ` [PATCH v7 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Usama Arif
2026-06-02 3:51 ` Oscar Salvador (SUSE)
2026-06-04 19:30 ` Pedro Falcato
2026-06-01 10:21 ` [PATCH v7 2/2] mm: use mapping_max_folio_order() for force_thp_readahead order Usama Arif
2026-06-01 16:22 ` Jan Kara
2026-06-04 19:33 ` Pedro Falcato
2026-06-01 23:10 ` Andrew Morton [this message]
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