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X-Received-From: 2607:f8b0:4864:20::241 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Richard Henderson , QEMU Developers , Niek Linnenbank , qemu-arm , Paolo Bonzini , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 26 Feb 2020 at 08:44, Philippe Mathieu-Daud=C3=A9 wrote: > > On 2/26/20 9:41 AM, Peter Maydell wrote: > > On Tue, 25 Feb 2020 at 23:08, Niek Linnenbank wrote: > > > >> Just now I was working on some small fixes for the cubieboard machine = and rebasing my Allwinner H3 branches. > >> While doing some testing, I noticed that suddenly the machines were mu= ch slower than before. > >> I only see this happening when I rebase to this commit: > >> ca6155c0f2bd39b4b4162533be401c98bd960820 ("Merge tag 'patchew/2020= 0219160953.13771-1-imammedo@redhat.com' of https://github.com/patchew-proje= ct/qemu into HEAD") > > > > Yeah, I noticed a slowdown yesterday as well, but haven't tracked it do= wn > > as yet. The first thing would be to do a git bisect to try to narrow > > down what commit caused it. > > My guess: biggest chunk of memory is the DRAM, registered as "fast RAM" > by QEMU, but the SoCs provide SRAM which is supposed to be faster. Not > anymore with QEMU. And Linux try to use the SRAM when possible. Doesn't sound very likely to me: generally Linux doesn't use random small lumps of SRAM, it just goes for whatever the dtb says is the main RAM, usually DRAM. And I thought that all RAM blocks within QEMU performed the same? >From the commit that Howard tracked down as the cause it looks like an ordering-of-actions issue in vl.c where something that was assuming memory-size-related stuff was set up is now running before those variables/fields are set correctly rather than after ? thanks -- PMM