From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (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 C24BA1F1932 for ; Fri, 19 Jun 2026 11:57:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781870277; cv=none; b=USvg5FNPJNuDYQp1uRKe9iUa7PIbM4plxMMTQsoWSVC5Bt0G8XwA8wLfKCx8rOYKAMTSMuqYQeXkbpY9VVsYLKdQbovUf40BReECe9FByrWYlhKGbkD8+qh1MpcLkjIpig9cvupbZxnLJ7SUm8hiT+lmZBRj6+CkX0rug4qMDsE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781870277; c=relaxed/simple; bh=wyhkemWNQpWjGxa/C2PnC8oIGT28ZI7NMGInkEie8vE=; h=Mime-Version:Content-Type:Date:Message-Id:To:Cc:Subject:From: References:In-Reply-To; b=hBriB1pREbEo7hUy91Jt3EPCpfQSOqJ0DpzMKa1GeMQyCyKrf5E+htofr4CYeElIokPkBLnHXMdMTgy8EkEtvx+lTQ1BrTg/7c2DNTP4ZGa9yjic8/mnbKy96X5qHM2a22V1Y/cearetVj8GRVy+xDVvclUYYnNSwmaBisdWjwo= 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=qQUYWDF3; arc=none smtp.client-ip=91.218.175.186 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="qQUYWDF3" Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781870263; 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=wftliC1LQ6z9VS1Gw5TysYxVhKRYeesey3bP0ol5Avg=; b=qQUYWDF3+qK8Youd5mWL5OSayVDCQc7sH6PPvGQhfyxa9pcZi3OvfCDvkSPhBx6ULmXnDY ysHy9TRSNVAdPxtbcopzGMXib8jKqMynp2WmE46jofyPIXckB/hSRrU8biBNnlOxkXjsDK xQcfgnKGWSwIMYnqGWgtr42osPzhabs= Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 19 Jun 2026 11:57:39 +0000 Message-Id: To: "Hao Ge" , "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" , , , Subject: Re: [PATCH] mm/page_alloc: unify __alloc_frozen_pages[_nolock]_noprof() X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "Brendan Jackman" References: <20260617-alloc-trylock-v1-1-83fd7858832e@google.com> <2399b3ad-4eac-4a14-94c3-27e9f07972a1@kernel.org> <45fcc57a-ec8d-46d6-9c28-065d001c081f@linux.dev> In-Reply-To: <45fcc57a-ec8d-46d6-9c28-065d001c081f@linux.dev> X-Migadu-Flow: FLOW_OUT On Thu Jun 18, 2026 at 2:22 AM UTC, Hao Ge wrote: > > 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=E2=80=AFAM 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 renam= e 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 on= ly >>>>> 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 t= o >>>>> 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 seri= es. Oh, I just took a look and it's a bit more fiddly than I thought because alloc_tag.c is actually in lib/ not mm/.=20 How did you tackle that, can you share your implementation? It would be nice if we can avoid exposing alloc_flags in gfp.h.