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Sat, 4 Apr 2026 02:25:25 -0400 (EDT) Date: Sat, 4 Apr 2026 08:25:23 +0200 From: Greg KH To: Salvatore Dipietro Cc: dipietro.salvatore@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH 1/1] iomap: avoid compaction for costly folio order allocation Message-ID: <2026040413-greedily-backlash-298d@gregkh> References: <20260403193201.30479-1-dipiets@amazon.it> <20260403193201.30479-2-dipiets@amazon.it> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260403193201.30479-2-dipiets@amazon.it> On Fri, Apr 03, 2026 at 07:32:01PM +0000, Salvatore Dipietro wrote: > Commit 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") > introduced high-order folio allocations in the buffered write > path. When memory is fragmented, each failed allocation triggers > compaction and drain_all_pages() via __alloc_pages_slowpath(), > causing a 0.75x throughput drop on pgbench (simple-update) with > 1024 clients on a 96-vCPU arm64 system. > > Strip __GFP_DIRECT_RECLAIM from folio allocations in > iomap_get_folio() when the order exceeds PAGE_ALLOC_COSTLY_ORDER, > making them purely opportunistic. > > Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") > Cc: stable@vger.kernel.org > Signed-off-by: Salvatore Dipietro > --- > fs/iomap/buffered-io.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.