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 6FAB41632E7 for ; Thu, 18 Jun 2026 02:23:55 +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=1781749438; cv=none; b=YBeF911PZkKwyTfPeeR+sW+udJaLFDtcgtx3/vqGAPgGImMiAc7Nhbqp0jSwnwMzKgdxDrFOfPk2fxG3oHD/g2Yhfa0B2j2th80zTFDfR0NH7raaxqZOtstlh5qbTG6A3NTQ+TezLpoYtvxVC1xgwg4cxWg5sB1MFvlBWCAQruw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781749438; c=relaxed/simple; bh=RFJlpQy9TvmKjPUb9OCSTSfYfIKV9NtKRPpE3ThjANQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Z/lifdhOj4cSicfHNTe9mSmFUzfq+M841wDDZGvK3bpHbpwNI8pGOxtXgGyoAhQVFjqVK+QAEuFm4+K23/lkzJQrqa6feYCmH9ChBJROG0vsuzpo3REhyscKmRsdgMXjNJp7CJtYunHuVWKIy1L+u5LgAm0YPKJ3PiBI0Rvt6lw= 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=O3UfvT/1; 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="O3UfvT/1" Message-ID: <45fcc57a-ec8d-46d6-9c28-065d001c081f@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781749433; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PfUm8af/m5Y+JvEu5zk0BWRI+9j/PXO2lmh/Wz0+tsw=; b=O3UfvT/1MKiXtNvGidZMkfJ5JuNdkyR8S+zPPWv9pS9CANHCtAc95ka7/DKnM/iGfcbWVb Ftrei5j/5KT11Bnfcu/K0q/mftP6aEgB40P687LESlZvdqrqD6vOCwMqayeuc19JuU2S7s mOQKdiH/a8oeTVe0QRkhZDezTFs9iMU= Date: Thu, 18 Jun 2026 10:22:47 +0800 Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] mm/page_alloc: unify __alloc_frozen_pages[_nolock]_noprof() To: Brendan Jackman , Suren Baghdasaryan , "Vlastimil Babka (SUSE)" Cc: Brendan Jackman , Andrew Morton , Michal Hocko , Johannes Weiner , Zi Yan , Muchun Song , Oscar Salvador , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Alexei Starovoitov , "Harry Yoo (Oracle)" , Gregory Price , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev References: <20260617-alloc-trylock-v1-1-83fd7858832e@google.com> <2399b3ad-4eac-4a14-94c3-27e9f07972a1@kernel.org> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 2026/6/18 01:14, Brendan Jackman wrote: > On Wed Jun 17, 2026 at 4:49 PM UTC, Suren Baghdasaryan wrote: >> On Wed, Jun 17, 2026 at 9:39 AM Vlastimil Babka (SUSE) >> wrote: >>> +Cc Alexei >>> >>> On 6/17/26 17:29, Brendan Jackman wrote: >>>> Currently the core allocator code is controlled by ALLOC_NOLOCK, but the >>> It's not, it's ALLOC_TRYLOCK! Thanks for proving that we need to rename it >>> to ALLOC_NOLOCK: >>> >>> https://lore.kernel.org/all/DJ9QPTO2WXNB.10E88ZHWRDHB0@gmail.com/ >>> >>> So you just won the job to do the rename :) I think it should be done before >>> this patch, so that the new usages and other _trylock names introduced here >>> can be done as _nolock outright. > Ack. I'll aim to send that tomorrow once Sashiko has caught up. > >>>> main entry point function is significantly different from the normal >>>> __alloc_frozen_pages_nolock(), this is tiring when reading the code. >>>> >>>> Plumb the ALLOC_NOLOCK control one layer up in the call stack: create >>>> an alloc_flags argument to __alloc_frozen_pages_nolock() (which is only >>>> exposed to mm/) and then turn the nolock variant into a thin wrapper >>>> that just sets that flag (as well as handling NUMA_NO_NODE, similar to >>>> how some of the wrappers in gfp.h do). >>>> >>>> Rationale that this doesn't change anything: >>>> >>>> 1. Simple bits: A bunch of the nolock-specific handling is just moved to >>>> the new alloc_order_allowed(), alloc_trylock_allowed() and >>>> gfp_trylock. >>>> >>>> 2. __alloc_frozen_pages_noprof() has some extra logic that wasn't >>>> previously in the nolock variant: >>>> >>>> a. Application of gfp_allowed_mask; this only affects early boot, and >>>> only flags that affect the slowpath get changed here. >>>> >>>> b. Application of current_gfp_context() - also only affects the >>>> slowpath >>>> >>>> 3. The slowpath itself: this is now just explicitly skipped under >>>> !ALLOC_TRYLOCK. >>> I'll have to ponder it more closely. >>> >>>> Ulterior motive: adding an alloc_flags arg to the allocator's >>>> mm-internal entrypoint can later be used to do more allocation >>>> customisation without needing to create new GFP flags. >>> Ack. >> I think this change might also help us in removing __GFP_NO_CODETAG > Nice, this actually looks trivial? I can probably just tack it onto the > v2 for this patch/series. > >> introduced in [1] and being the only user of __GFP_NO_OBJ_EXT once >> Vlastimil's patchset removing other __GFP_NO_OBJ_EXT users lands. >> CC'ing Hao as he is brainstorming ways to remove __GFP_NO_CODETAG, and >> this might be the answer. Hi Brendan, Suren, Thanks for CC'ing me, Suren. This is indeed a viable approach and I believe it brings us one step closer to removing __GFP_NO_CODETAG entirely. Brendan, I'd actually put together a rough local implementation earlier with mostly the same core idea as yours, and this change would indeed be minimal based on your patch. Thanks a lot for being interested in tacking this into your v2 patch series. Thanks Best Regards Hao >>> Besides the need to ponder unintended effects, mostly LGTM. Just not a fan >>> of the hardcoded '0' passed at various places. In the slab variant of this >>> (the thread I've linked above) I went with SLAB_ALLOC_DEFAULT, so you can do >>> e.g. ALLOC_DEFAULT here? > Yup ALLOC_DEFAULT sounds fine to me. > > Thanks for the reviews as always.