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b=J0JkL9lBEj+bJEpZsIMnlGLtbUGzsEhtTpEMsGQJTOCOUYy06bSt7zPsjyWsAXFwb MHklrZv1rxUK32wVEHuxVecXHnFC28Zf+syXCbZxl4o+2ZCqwEzZ0OmfIqL/pC/s4U D0W2bFI+4YI7Dwz1f1ZFdoeAum8+cXFjS9SZQpV633decb5028zHizIuiQm+6syd5k 6AlJNxhH3kG2oCJsRStWtRLkYPZbQvgBwwVz/+heraTuhG02bALRVn0FtM2KZR19So Mxzm/BMgyGiWNMW13L++5pAkOrxnzmepI7S8VEx3EvmkJ6hrQJ6WZ8N6goezeULx89 ubAIo3cyjp1Gg== Date: Wed, 26 Nov 2025 11:00:21 -0800 From: Namhyung Kim To: Peter Zijlstra Cc: Vlastimil Babka , Xianying Wang , akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , linux-perf-users@vger.kernel.org Subject: Re: [BUG] WARNING in __alloc_frozen_pages_noprof Message-ID: References: <4cb9f727-734b-43fa-92d2-80559df76c84@suse.cz> <20251126111921.GU4067720@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20251126111921.GU4067720@noisy.programming.kicks-ass.net> X-Rspamd-Queue-Id: F40E416001A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bgbmhini7z8cm4rce8kuxchdf9at1595 X-HE-Tag: 1764183626-694809 X-HE-Meta: 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 DvWz+kmI dM8rvW7/B4h3Cxxty5vJ8WGtZ+zd2B387g6UMYah44Xd3GAmF1bw/0HJgLiA9JJKyhhGGFwk0ERDtI7E/hrdW+Ww4p5nekan55Gn07WPF1leqyxMFYI5Goy3zWg5rgTMV+ez7esUeUrmQvtAicEx8QX5UNYUvxddbVhsJa0lKgNvnUvVi+veZ2cA4uEbpXNDTgOzrc7/niFQ+XuWueVctM90sWqYVo91N6tkLsJlqSrx+Vu1bXQstsZv9YArVQpOtpLChyG8gblP84Xn2bAz1oOILttpTR8qNNnUaZ1PHuAwxjh1R3QjSz+oWEmf5LIiT2iW6I/hjHDYssO9SSTSBcZoDWQ== 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: List-Subscribe: List-Unsubscribe: Hello, On Wed, Nov 26, 2025 at 12:19:21PM +0100, Peter Zijlstra wrote: > On Wed, Nov 26, 2025 at 10:46:38AM +0100, Vlastimil Babka wrote: > > +CC perf people as AFAIU the problem originates there. Should the limit > > be lowered, or the allocations e.g. switched to kvmalloc, to avoid > > requesting impossibly high order allocations? > > > > /* > > * There are several places where we assume that the order value is sane > > * so bail out early if the request is out of bound. > > */ > > if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) > > return NULL; > > > > > > > > On 11/19/25 10:07 AM, Xianying Wang wrote: > > > Hi, > > > > > > I hit the following warning in the page allocator when opening a perf > > > event with callchain sampling after increasing > > > kernel.perf_event_max_stack.This warning can be triggered by first > > > writing a large value into kernel.perf_event_max_stack and then > > > opening a perf event with callchain sampling enabled. > > > > > > The reproducer does two things: > > > > > > 1) It writes a large (but still accepted) value to the sysctl: > > > > > > echo 0x40132 > /proc/sys/kernel/perf_event_max_stack > > > > > Yeah, that is far too large. I suppose the actual max is somewhere near > 8k, which would give 64k data for just the callchain -- given that a > single perf buffer entry is limited to 64k (IIRC) and all that. Right, we have u16 size in struct perf_event_header. Thanks, Namhyung