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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779987413; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ODVkNxNqhWTJOtKAdxjrGaooJs+N26LEMo3Jm83wAZk=; b=RtxHGihuDflh4ac8Bae6kMhwJa9BvxP/Jh+0u/dFzZDYk+edYYoavV2mvjkuya5R0K6zcv lW0HhTgfQ9mJMowmgn2+H16hdpHyaBmJp6WfvZz9s3ybjlOAIHleG1FVI6h8CZz9PVORtg DDMAiJOC18RySHWHtTghSsEOWVd3dQY= From: Usama Arif To: Andrew Morton , david@kernel.org, willy@infradead.org, ryan.roberts@arm.com, linux-mm@kvack.org Cc: r@hev.cc, jack@suse.cz, Andrew Donnellan , 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 , 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 , wilts.infradead.org@kvack.org, "linux-fsdevel@vger.kernel.l"@kernel.org, ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com, Usama Arif Subject: [PATCH v6 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Date: Thu, 28 May 2026 09:55:19 -0700 Message-ID: <20260528165635.2068012-2-usama.arif@linux.dev> In-Reply-To: <20260528165635.2068012-1-usama.arif@linux.dev> References: <20260528165635.2068012-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Stat-Signature: bmfa1ogpc8efa553hxzuhrf54gcu4otf X-Rspamd-Queue-Id: A75732000C X-Rspam-User: X-HE-Tag: 1779987415-587762 X-HE-Meta: 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 7CyXk4YR TycrcZstg4AUqhLP4Khlil0TS/OhwCUmnRhOm4rzdIZNjZASFM0SBWFuFUuTgge1jSEEL7JvQwpz6gajEafxfQzcciDTEik6LP7BWAPhXNqSqJAaEFh2K5IZyjERFgjDYAY8rAlfmo6q4a5U50ugp6K42pQ7u6khHT7yJ/+B5YpS459Bnc6XMg5U3Z9Z6Kx18VAo+SOeVM/QqmKnJV+GeROtdzl56qrccgiSLNUg+wDes+lZMciPwI7VFvgPocVlBKuvbXR6CuJQlL/bztO043oriDIdu0hMTUpOE9h2QkaG58wf7S/oyz0LjiA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The mmap_miss heuristic is intended to stop speculative mmap readahead when a file looks like a random-access workload. That does not fit the VM_EXEC path very well. VM_EXEC readahead is already constrained differently from ordinary mmap read-around: it is bounded by the VMA, uses exec_folio_order() to choose an order useful for executable mappings, and sets async_size to 0 so it does not create follow-on readahead. When VM_HUGEPAGE is also present, the larger readahead is an explicit userspace opt-in. The mmap_miss counter is decremented from cache-hit paths in do_async_mmap_readahead() and filemap_map_pages(). Those paths are not always enough to balance the synchronous miss increments for executable mappings. In particular, when fault-around is effectively disabled, such as configurations where fault_around_pages is 1, filemap_map_pages() is not reached from the fault path. The counter can then become a stale throttle for VM_EXEC mappings and suppress the readahead behavior that the executable-specific path is trying to provide. Skip both mmap_miss increments and decrements for VM_EXEC mappings, matching the existing VM_SEQ_READ treatment and keeping the counter accounting symmetric. Signed-off-by: Usama Arif Reviewed-by: Jan Kara Reviewed-by: Kiryl Shutsemau (Meta) --- mm/filemap.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index cca20e350c95..a16b33e0fc71 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3339,7 +3339,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) } } - if (!(vm_flags & VM_SEQ_READ)) { + if (!(vm_flags & (VM_SEQ_READ | VM_EXEC))) { /* Avoid banging the cache line if not needed */ mmap_miss = READ_ONCE(ra->mmap_miss); if (mmap_miss < MMAP_LOTSAMISS * 10) @@ -3434,12 +3434,12 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, * times for a single folio and break the balance with mmap_miss * increase in do_sync_mmap_readahead(). * - * VM_SEQ_READ mappings skip the mmap_miss increment in + * VM_SEQ_READ and VM_EXEC mappings skip the mmap_miss increment in * do_sync_mmap_readahead(), so skip the decrement here as well to * keep the counter symmetric. */ if (likely(!folio_test_locked(folio)) && - !(vmf->vma->vm_flags & VM_SEQ_READ)) { + !(vmf->vma->vm_flags & (VM_SEQ_READ | VM_EXEC))) { mmap_miss = READ_ONCE(ra->mmap_miss); if (mmap_miss) WRITE_ONCE(ra->mmap_miss, --mmap_miss); @@ -3941,14 +3941,14 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, * Don't decrease mmap_miss in this scenario to make sure * we can stop read-ahead. * - * VM_SEQ_READ mappings skip the mmap_miss increment in - * do_sync_mmap_readahead(), so skip the decrement here as - * well to keep the counter symmetric. + * VM_SEQ_READ and VM_EXEC mappings skip the mmap_miss + * increment in do_sync_mmap_readahead(), so skip the + * decrement here as well to keep the counter symmetric. */ if ((map_ret & VM_FAULT_NOPAGE) && !(vmf->flags & FAULT_FLAG_TRIED) && !folio_test_workingset(folio) && - !(vma->vm_flags & VM_SEQ_READ)) { + !(vma->vm_flags & (VM_SEQ_READ | VM_EXEC))) { unsigned short mmap_miss; mmap_miss = READ_ONCE(file->f_ra.mmap_miss); -- 2.52.0