From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta1.migadu.com (out-186.mta1.migadu.com [95.215.58.186]) (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 E23C138E8C3 for ; Mon, 22 Jun 2026 08:33:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782117208; cv=none; b=fEJzjSCSrZYwll1fTmSxX+Nhz4WoBd4Cv6LtorC5WABfLt7xdPc7GFkldn1oMQYcHujBHPTIUFdiFcj4l4vOOdaRiBBP9MeFhKap90a5cFiOUkbV44YcKBKhz7Wi9rWGT8n6mJ+B1BfmoWOK0Coa0zMvBrVsj8cJsiLOlVwU2HU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782117208; c=relaxed/simple; bh=rJ9EqyZX+1uDH1xu352c0spmEyEZT9KSZXW7ls/HB/U=; h=Mime-Version:Content-Type:Date:Message-Id:Subject:From:To:Cc: References:In-Reply-To; b=IdMwHfY63FfV49Bh5Kra4WrHfdnMHH80MzjZGSnNv6AqzgZYCZSY03KPZSPapUEGmUtMfi3yMS9luhClSslr0g/76taZhFZhlC7TN7cq2zp9ZY5Z+XnYhJA92/y2yM7KusqwMhshtCx0YDh0ulDY479KBu+8X7Jxn/MldTJv1zQ= 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=FHQAc44n; arc=none smtp.client-ip=95.215.58.186 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="FHQAc44n" 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=1782117204; 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=KqsCQKkmRUVfBZPd9K730PqbM5N64wyAbDnC+li40Cw=; b=FHQAc44nNfvpZIk6Uesy9k4k9buuih+lxEV7l+zy54ZgveUwr+BgFoeslLQE75ak8UVx4M y7bVz8N0i/NrJh5F/0cTK/UcW17X8U94lzBuQX+qTpeGiy4CZJNXy5Eh7fIs3JrAJVIOfd lJhqrCFABYGLKPmVbs/XB8+wA4Q2SSA= Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 22 Jun 2026 08:33:12 +0000 Message-Id: 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" To: "Hao Ge" , "Suren Baghdasaryan" , "Brendan Jackman" Cc: "Vlastimil Babka (SUSE)" , "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" , , , References: <20260617-alloc-trylock-v1-1-83fd7858832e@google.com> <2399b3ad-4eac-4a14-94c3-27e9f07972a1@kernel.org> <45fcc57a-ec8d-46d6-9c28-065d001c081f@linux.dev> <267e070f-adc2-4f42-b528-746f852d9ef4@linux.dev> In-Reply-To: <267e070f-adc2-4f42-b528-746f852d9ef4@linux.dev> X-Migadu-Flow: FLOW_OUT On Mon Jun 22, 2026 at 1:58 AM UTC, Hao Ge wrote: > > On 2026/6/20 02:08, Suren Baghdasaryan wrote: >> On Fri, Jun 19, 2026 at 4:57=E2=80=AFAM Brendan Jackman >> wrote: >>> 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, b= ut the >>>>>>> It's not, it's ALLOC_TRYLOCK! Thanks for proving that we need to re= name 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 do= ne before >>>>>>> this patch, so that the new usages and other _trylock names introdu= ced 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 norm= al >>>>>>>> __alloc_frozen_pages_nolock(), this is tiring when reading the cod= e. >>>>>>>> >>>>>>>> Plumb the ALLOC_NOLOCK control one layer up in the call stack: cre= ate >>>>>>>> an alloc_flags argument to __alloc_frozen_pages_nolock() (which is= only >>>>>>>> exposed to mm/) and then turn the nolock variant into a thin wrapp= er >>>>>>>> that just sets that flag (as well as handling NUMA_NO_NODE, simila= r 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 mo= ved 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 b= oot, and >>>>>>>> only flags that affect the slowpath get changed here. >>>>>>>> >>>>>>>> b. Application of current_gfp_context() - also only affects t= he >>>>>>>> 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 t= he >>>>> 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, a= nd >>>>>> 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 s= eries. >>> Oh, I just took a look and it's a bit more fiddly than I thought becaus= e >>> alloc_tag.c is actually in lib/ not mm/. > > Hi Suren and Bredan > > >> One option is to move alloc_tag.c into mm/ (while keeping more generic >> codetag.c in lib/). From a quick look, that seems doable and probably >> the easiest approach. >> >>> How did you tackle that, can you share your implementation? It would be >>> nice if we can avoid exposing alloc_flags in gfp.h. > > First, I introduced the ALLOC_NO_CODETAG flag as shown below: > > @@ -1478,6 +1480,7 @@ unsigned int reclaim_clean_pages_from_list(struct= =20 > zone *zone, > =C2=A0#define ALLOC_HIGHATOMIC=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0x200= /* Allows access to=20 > MIGRATE_HIGHATOMIC */ > =C2=A0#define ALLOC_TRYLOCK=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 0x400 /* Only use spin_trylock in=20 > allocation path */ > =C2=A0#define ALLOC_KSWAPD=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 0x800 /* allow waking of kswapd,=20 > __GFP_KSWAPD_RECLAIM set */ > +#define ALLOC_NO_CODETAG=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0x1000 /* s= kip codetag tracking for this=20 > allocation */ > > > Then, mirroring __alloc_pages_noprof, we wrapped a helper function named= =20 > alloc_pages_noprof_notag. > > > @@ -5252,13 +5335,25 @@ struct page *__alloc_pages_noprof(gfp_t gfp,=20 > unsigned int order, > =C2=A0{ > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct page *page; > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 page =3D __alloc_frozen_pages_nopro= f(gfp, order, preferred_nid,=20 > nodemask); > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 page =3D __alloc_frozen_pages_nopro= f(gfp, order, preferred_nid,=20 > nodemask, 0); > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (page) > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 set_page_refcounted(page); > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return page; > =C2=A0} > =C2=A0EXPORT_SYMBOL(__alloc_pages_noprof); > > +struct page *alloc_pages_noprof_notag(gfp_t gfp, unsigned int order) > +{ > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct page *page; > + > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 page =3D __alloc_frozen_pages_nopro= f(gfp, order, numa_node_id(), NULL, > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 ALLOC_NO_CODETAG); > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (page) > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 set_page_refcounted(page); > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return page; > +} > +EXPORT_SYMBOL_GPL(alloc_pages_noprof_notag); > > > Lastly, we exported this function in gfp.h as shown below: > > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index 51ef13ed756e..ac6e837ac8c0 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -234,6 +234,9 @@ struct folio *__folio_alloc_noprof(gfp_t gfp,=20 > unsigned int order, int preferred_ > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 nodemask_t *nodemask); > =C2=A0#define __folio_alloc(...) alloc_hooks(__folio_alloc_noprof(__VA_A= RGS__)) > > +struct page *alloc_pages_noprof_notag(gfp_t gfp, unsigned int order); > +#define alloc_pages_notag(...)=20 > alloc_hooks(alloc_pages_noprof_notag(__VA_ARGS__)) > > > Hope this information helps you. Cool, thanks! On Friday I also tried doing it by just moving the .c file and that also seems to be pretty practical.=20