From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta1.migadu.com (out-174.mta1.migadu.com [95.215.58.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1111A2356CE for ; Wed, 20 Aug 2025 23:00:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755730807; cv=none; b=ZEGSY3lFu5OiBKrEaiV/8/O1jQCud5LOki5lK7EagVnfi3dJhOFqmTGoPXmPrfmtLVJ2L153d9IgdMneOdY9Y5Sg0DZ40381VqSyp1K03jnDnsl2iImXFz2XzPgL1RH3zUe6q7BnqzwHXEJS3ufevLOXJAMz80/Vpb7DFrzMzG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755730807; c=relaxed/simple; bh=x4K0iLjGZFeXuNimOGdOcEHhd2/2bbTeCrm3B72xoOk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=RvEe8aWh7S97i1NBT4NkdkIDTig4gwwzRlBXWVY9gbEGzh1TP1K89Bu/14stul8uIDncjrH3AAQgkfxbjFWzvOCegBZQOBeYseLSu7MJvLeck9/iIdGob2GLzzyMf1nha7W7KyvnBCsaNeaTqMXuoefyJ+TE0LqtrA24FOVf3iQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=U7l0i6CL; arc=none smtp.client-ip=95.215.58.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="U7l0i6CL" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1755730800; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=LwMfKt/z+b32Yog71y0IpHQR50ir1+SPpvMPlDiQyXM=; b=U7l0i6CLs6K5elGR2S9r3KYV+KT3KbqTIrQKQ4wXxtsjxNCdZjVBOTgvSdznS3eWHzCcNj yoXFsMF3+BeByV5AOH6oeYMWD8+Xc9fai/nBhrUKeCusI2O3ZuyRhw20Hzssg7XDCT743J cS0Oxf9asNw/vgky++prC0R8zDSg+4M= From: Roman Gushchin To: Kumar Kartikeya Dwivedi Cc: linux-mm@kvack.org, bpf@vger.kernel.org, Suren Baghdasaryan , Johannes Weiner , Michal Hocko , David Rientjes , Matt Bobrowski , Song Liu , Alexei Starovoitov , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 06/14] mm: introduce bpf_out_of_memory() bpf kfunc In-Reply-To: (Kumar Kartikeya Dwivedi's message of "Wed, 20 Aug 2025 11:34:39 +0200") References: <20250818170136.209169-1-roman.gushchin@linux.dev> <20250818170136.209169-7-roman.gushchin@linux.dev> Date: Wed, 20 Aug 2025 15:59:53 -0700 Message-ID: <87349loaza.fsf@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT Kumar Kartikeya Dwivedi writes: > On Mon, 18 Aug 2025 at 19:02, Roman Gushchin wrote: >> >> Introduce bpf_out_of_memory() bpf kfunc, which allows to declare >> an out of memory events and trigger the corresponding kernel OOM >> handling mechanism. >> >> It takes a trusted memcg pointer (or NULL for system-wide OOMs) >> as an argument, as well as the page order. >> >> If the wait_on_oom_lock argument is not set, only one OOM can be >> declared and handled in the system at once, so if the function is >> called in parallel to another OOM handling, it bails out with -EBUSY. >> This mode is suited for global OOM's: any concurrent OOMs will likely >> do the job and release some memory. In a blocking mode (which is >> suited for memcg OOMs) the execution will wait on the oom_lock mutex. >> >> The function is declared as sleepable. It guarantees that it won't >> be called from an atomic context. It's required by the OOM handling >> code, which is not guaranteed to work in a non-blocking context. >> >> Handling of a memcg OOM almost always requires taking of the >> css_set_lock spinlock. The fact that bpf_out_of_memory() is sleepable >> also guarantees that it can't be called with acquired css_set_lock, >> so the kernel can't deadlock on it. >> >> Signed-off-by: Roman Gushchin >> --- >> mm/oom_kill.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 45 insertions(+) >> >> diff --git a/mm/oom_kill.c b/mm/oom_kill.c >> index 25fc5e744e27..df409f0fac45 100644 >> --- a/mm/oom_kill.c >> +++ b/mm/oom_kill.c >> @@ -1324,10 +1324,55 @@ __bpf_kfunc int bpf_oom_kill_process(struct oom_control *oc, >> return 0; >> } >> >> +/** >> + * bpf_out_of_memory - declare Out Of Memory state and invoke OOM killer >> + * @memcg__nullable: memcg or NULL for system-wide OOMs >> + * @order: order of page which wasn't allocated >> + * @wait_on_oom_lock: if true, block on oom_lock >> + * @constraint_text__nullable: custom constraint description for the OOM report >> + * >> + * Declares the Out Of Memory state and invokes the OOM killer. >> + * >> + * OOM handlers are synchronized using the oom_lock mutex. If wait_on_oom_lock >> + * is true, the function will wait on it. Otherwise it bails out with -EBUSY >> + * if oom_lock is contended. >> + * >> + * Generally it's advised to pass wait_on_oom_lock=true for global OOMs >> + * and wait_on_oom_lock=false for memcg-scoped OOMs. >> + * >> + * Returns 1 if the forward progress was achieved and some memory was freed. >> + * Returns a negative value if an error has been occurred. >> + */ >> +__bpf_kfunc int bpf_out_of_memory(struct mem_cgroup *memcg__nullable, >> + int order, bool wait_on_oom_lock) > > I think this bool should be a u64 flags instead, just to make it > easier to extend behavior in the future. I like it, will change in the next version. Thanks for the idea and also for reviewing the series!