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[185.219.167.24]) by smtp.gmail.com with ESMTPSA id g11-20020a056402428b00b004722d7e8c7csm6768666edc.14.2023.01.11.22.07.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Jan 2023 22:07:27 -0800 (PST) Message-ID: <7aa90802-d25c-baa3-9c03-2502ad3c708a@kernel.org> Date: Thu, 12 Jan 2023 07:07:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Content-Language: en-US To: Pedro Falcato Cc: Paolo Bonzini , kvm@vger.kernel.org, Andrew Morton , mm , yuzhao@google.com, Michal Hocko , Vlastimil Babka , shy828301@gmail.com References: From: Jiri Slaby Subject: Re: Stalls in qemu with host running 6.1 (everything stuck at mmap_read_lock()) In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 949D0100006 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: pt8mdmeyu6to5bcb9jpjjkuh17h6ti44 X-HE-Tag: 1673503649-497676 X-HE-Meta: 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 DFRNmfBC fBzsVVFSQtiK3yUZkLp1lUfgQkOApYsNNb5bZdR4NXI/soik45c6/VH1vGtvhyfiZY6rWlqwIEy1/1bGiFokW0hILU/m+ouwXcynfH+0k1+LU6pPfrWsms1enkRH6bGq4l9lm/rgoP7+SODL6qDBesPvR3vN0A1CPnzwIdGJZzmqasMVAFt3whxrA7Oru/ozWuilm/dEB5ODI+QbTDQSmiNccvd2uD4tzIDdo5USQtKv7mRcu7yn32O/z8UyKi5hDdv2j6eOTMo3s2GOtASqfarke/yw18/QtM1YWLFmbRji2mGM8zv/Zs45WKF7Ce+wQ099Oc1vV1pXQtYYr36NsmLFsCQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, On 12. 01. 23, 1:37, Pedro Falcato wrote: > I just want to chime in and say that I've also hit this regression > right as I (Arch) updated to 6.1 a few weeks ago. > This completely ruined my qemu workflow such that I had to fallback to > using an LTS kernel. > > Some data I've gathered: > 1) It seems to not happen right after booting - I'm unsure if this is > due to memory pressure or less CPU load or any other factor +1 as I wrote. > 2) It seems to intensify after swapping a fair amount? At least this > has been my experience. I have no swap. > 3) The largest slowdown seems to be when qemu is booting the guest, > possibly during heavy memory allocation - problems range from "takes > tens of seconds to boot" to "qemu is completely blocked and needs a > SIGKILL spam". +1 > 4) While traditional process monitoring tools break (likely due to > mmap_lock getting hogged), I can (empirically, using /bin/free) tell > that the system seems to be swapping in/out quite a fair bit Yes, htop/top/ps and such are stuck at the read of /proc//cmdline as I wrote (waiting for the mmap lock). > My 4) is particularly confusing to me as I had originally blamed the > problem on the MGLRU changes, while you don't seem to be swapping at > all. > Could this be related to the maple tree patches? Should we CC both the > MGLRU folks and the maple folks? > > I have little insight into what the kernel's state actually is apart > from this - perf seems to break, and I have no kernel debugger as this > is my live personal machine :/ > I would love it if someone hinted to possible things I/we could try in > order to track this down. Is this not git-bisectable at all? I have rebooted to a fresh kernel which 1) have lockdep enabled, and 2) I have debuginfo for. So next time this happens, I can print held locks and dump a kcore (kdump is set up). regards, -- js suse labs