From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 AABDA25B0AF for ; Mon, 22 Jun 2026 01:59:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782093549; cv=none; b=KWcm4f6lLM0TmIPCG5WMM8UwyjGSmYz7l0rxkOIlVkaNc2+xv5lKqicX0sMscbGkyE/vlcNmhgyLmFwk4GRmy0y37LQcZ1XK85Nntg+N4prCz/HBsWqkiLXTpJAYtP7skhf4UQJZdweAeVBKm2LTpzvuYypXB4fISBFl3Ko340Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782093549; c=relaxed/simple; bh=coW+ZqFoBHE+c7dosS4f+l6eRFfW5LPu06hW+62223k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ePsFeWOJxEzj8uE3q4E+Jn0fq7k8FcOpFS4Sub4M2GHg/nUsB+hcLxRduWfIHNBORh8rYGQsZwTsm+Xjho8c7fZi8Shr5RMQCOLjQ0qa2sEJh1wcBxejCMNymVhWokWEfiKcZd0Y766BDpi5ub4moLW9yqoxKYkfu71ozp/iU1g= 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=NxFaFZSm; arc=none smtp.client-ip=95.215.58.182 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="NxFaFZSm" Message-ID: <267e070f-adc2-4f42-b528-746f852d9ef4@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782093535; 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=0qpRzlSyLktZxcLZDCE/8RBM2MX99p//TZMgpKeEF9c=; b=NxFaFZSmEW+ZWMeELNcIGCdhQ61H6KXKppMDcfRpFas7ME15wP+WUEtZZQoKET/vfzZHJM T4aMhPb8ktKruOCy6L+uoJ7VUXfLkbV3gpbyN6nq+y+oAc8YqFniPixLSLsy3WzjQKg4NR VyI6gSHfcIUoVL1ANtxXoVvryXQrYd8= Date: Mon, 22 Jun 2026 09:58:00 +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: 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 , 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> <45fcc57a-ec8d-46d6-9c28-065d001c081f@linux.dev> 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 2026/6/20 02:08, Suren Baghdasaryan wrote: > On Fri, Jun 19, 2026 at 4:57 AM 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 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. >> 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/. 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 zone *zone,  #define ALLOC_HIGHATOMIC       0x200 /* Allows access to MIGRATE_HIGHATOMIC */  #define ALLOC_TRYLOCK          0x400 /* Only use spin_trylock in allocation path */  #define ALLOC_KSWAPD           0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ +#define ALLOC_NO_CODETAG       0x1000 /* skip codetag tracking for this allocation */ Then, mirroring __alloc_pages_noprof, we wrapped a helper function named alloc_pages_noprof_notag. @@ -5252,13 +5335,25 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order,  {         struct page *page; -       page = __alloc_frozen_pages_noprof(gfp, order, preferred_nid, nodemask); +       page = __alloc_frozen_pages_noprof(gfp, order, preferred_nid, nodemask, 0);         if (page)                 set_page_refcounted(page);         return page;  }  EXPORT_SYMBOL(__alloc_pages_noprof); +struct page *alloc_pages_noprof_notag(gfp_t gfp, unsigned int order) +{ +       struct page *page; + +       page = __alloc_frozen_pages_noprof(gfp, order, numa_node_id(), NULL, +                                          ALLOC_NO_CODETAG); +       if (page) +               set_page_refcounted(page); +       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, unsigned int order, int preferred_                 nodemask_t *nodemask);  #define __folio_alloc(...) alloc_hooks(__folio_alloc_noprof(__VA_ARGS__)) +struct page *alloc_pages_noprof_notag(gfp_t gfp, unsigned int order); +#define alloc_pages_notag(...) alloc_hooks(alloc_pages_noprof_notag(__VA_ARGS__)) Hope this information helps you. Thanks Best Regards Hao