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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780309345; 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=PvRsohE/ZO3afbXRx9ClOgEAbzgQczwO49YoCB7UQqiTfEVBmtIxaF8Vwuow2kGr0loz9v 4wQPHODBVox1noVmxIaEZhk4PUwfCGWuvg+Uu3skr76sAsSqd72Z2jFbLzJ5KIADisNOXt uXoCMcINK8Ff2a53qPVmFtSnw/S+72g= From: Usama Arif To: Andrew Morton , david@kernel.org, willy@infradead.org, ryan.roberts@arm.com, linux-mm@kvack.org Cc: pfalcato@suse.de, 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 , ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com, Usama Arif Subject: [PATCH v7 1/2] mm: bypass mmap_miss heuristic for VM_EXEC readahead Date: Mon, 1 Jun 2026 03:21:17 -0700 Message-ID: <20260601102205.3985788-2-usama.arif@linux.dev> In-Reply-To: <20260601102205.3985788-1-usama.arif@linux.dev> References: <20260601102205.3985788-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C09534000B X-Stat-Signature: 3s8z38cesbfokp751dgeui96quzkgfet X-HE-Tag: 1780309346-875795 X-HE-Meta: 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 pSrgPIKU UWjc3DRBlVBC+uBeoelSeMKpLMYllfyxFsbXatspEvbZAU6cA8U/IwKTYtbSKLaZLVd+bqmmgRl/Cg3MKzP9RAucrPd/TW40bwb6FTdXMLk6//JGD30I3eFSY4OdKIONmDGcXFwj/PvyJN8SWRi/1tt4uD1jUH6Epb2KLbR2BYi7Y5AIUusMTMN6kHOwmRC9w96bRGm9h7dX5UK7SfvB1OVs9mJAuiSAX3piXf/ESYYijEKDlSSBmpXXr1Dr4ApyiH7uX4dQdFLDfMXk/CF1Taf7fOYrK/EnqVq2pDszum7DZmuZbJvmI+0eM3P7xSmIQ/a9sAwGkCtpNXCJAxvFJlLC+Fp8ZyEfT22/7 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