From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A0CEE1A4F2F; Mon, 15 Jun 2026 09:02:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781514127; cv=none; b=RBLhLDTzzkC4XZ36HMeVzmZAsacDboa+sc7cw5KbbZ/C+vWao2T09ughcXWdIOU+vGRWXShA2dM4kC8FteeSsoZadHGULHF0EA7YelG0rHLSVC8p2OWQFdrjhAGUkiIpqnjvQEz0/BDXnsnaZusWZ3YhZxmviPndwRDwAoX/z0A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781514127; c=relaxed/simple; bh=eYO33OZYyxYtKwg4xXi5walByUVR1rAPD3k36LxnZc8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fXnpcjOMQvlTzHY72Ka+0V2UqykhrBXGSetbNc3wHF54y3y4AhL5xeaxrWm9hJi3vPxp9tyKfHizmdIxR6HJmiB83ncJzSK1ErOHVzIArzuGYumP4eHTZQ7BafLC7/4clg0IZ8wgFe6hFImSg7F7ICov4iJmOJZMU0p74yUBR30= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bpOCPu9c; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bpOCPu9c" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D61E71F000E9; Mon, 15 Jun 2026 09:02:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781514126; bh=zejvIfX8d2dRdR2mAJ04OI+CXDIR6kMQOBHLrkrQTuY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=bpOCPu9cAnQ49Uo92ymBgaDMsNNkCNFKwGJhICCG+otI4FMV/1oOM9BbFmEiw5Em4 C8wyRuso85zHacKQClkoVbhC99Qsbm8cmYaHrJ49uXB1J/tYEK+rCvNXsvrecquD7J kVgQwxtFU+5aDWA/ytr87bu917cKElEi7bbwLi+D91RJgEQO4cmrM9yOVBM4Hfxx9P SG93yjMZJnEoUuUMlo4c6fyG1UZFJuLRJfx5bN00r2+sriy+T6V/7PrtSWCk7LGuwk KXVr9X83dNSbMhpQ+2NqtyD41/ZR7kSIQyPYaVUtRUYg9VfALr3666VqLlO3RG9MTk pVT8qdIw+QhdQ== Message-ID: Date: Mon, 15 Jun 2026 11:02:01 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/16] mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK Content-Language: en-US To: Alexei Starovoitov , Suren Baghdasaryan Cc: Hao Li , Harry Yoo , Christoph Lameter , David Rientjes , Roman Gushchin , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Michal Hocko , Shakeel Butt , Alexander Potapenko , Marco Elver , Dmitry Vyukov , kasan-dev , linux-mm , LKML , "open list:CONTROL GROUP (CGROUP)" References: <20260610-slab_alloc_flags-v2-0-7190909db118@kernel.org> <20260610-slab_alloc_flags-v2-5-7190909db118@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/15/26 04:16, Alexei Starovoitov wrote: > On Sun, Jun 14, 2026 at 7:01 PM Suren Baghdasaryan wrote: >> >> On Thu, Jun 11, 2026 at 8:50 PM Hao Li wrote: >> > >> > On Wed, Jun 10, 2026 at 05:40:07PM +0200, Vlastimil Babka (SUSE) wrote: >> > > Similarly to the page allocators, introduce slab-allocator specific >> > > alloc flags that internally control allocation behavior in addition to >> > > gfp_flags, without occupying the limited gfp flags space. >> > > >> > > Introduce the first flag SLAB_ALLOC_TRYLOCK that behaves similarly to >> > > page allocator's ALLOC_TRYLOCK and will be used to reimplement >> > > kmalloc_nolock()'s "!allow_spin" behavior. That currently relies on >> > > gfpflags_allow_spinning() and thus the lack of both __GFP_RECLAIM flags, >> > > importantly __GFP_KSWAPD_RECLAIM. This can give false-positive results >> > > e.g. in early boot with a restricted gfp_allowed_mask. >> > > >> > > Also introduce alloc_flags_allow_spinning() to replace the usage of >> > > gfpflags_allow_spinning(). >> > > >> > > Start using alloc_flags and the new check first in alloc_from_pcs() and >> > > __pcs_replace_empty_main(). This means some slab allocations that were >> > > falsely treated as kmalloc_nolock() due to their gfp flags will now have >> > > higher chances of succeed, and this will further increase with followup >> >> nit: I think it should be either "higher chances of succeess" or >> "higher chances to succeed". success it is >> >> > > changes. >> > > >> > > Remove a WARN_ON_ONCE() from refill_objects() as it's now legitimate to >> > > reach it from a slab allocation that's not _nolock() and yet lacks >> > > __GFP_KSWAPD_RECLAIM for other reasons. >> > > >> > > Signed-off-by: Vlastimil Babka (SUSE) >> > > --- >> > >> > Reviewed-by: Hao Li >> >> I would call SLAB_ALLOC_TRYLOCK something like SLAB_ALLOC_NOSPIN or >> SLAB_ALLOC_NOLOCK but naming is hard and I don't claim myself to be >> good at it. So, feel free to adopt my suggestion if you like it or >> ignore it otherwise. >> >> Reviewed-by: Suren Baghdasaryan > > Just noticed "trylock" in the #define SLAB_ALLOC_TRYLOCK > > Please call it SLAB_ALLOC_NOLOCK. > > Initial api was using 'trylock' name and it was a mistake, > since people assumed normal spin_trylock() like semantics. > "trylock" implies that it fails under contention > and retry is a normal next step. It's not the case. > No one should be retrying. That's why the final api was kmalloc_nolock(). > So please keep this important distinction in the name. > SLAB_ALLOC_NOLOCK should mean that spinning locks > should not be taken. It should not mean "just go to trylock everywhere". Eh, ok then, will change to SLAB_ALLOC_NOLOCK. Even though it's mostly internal. So next thing we change page allocator's ALLOC_TRYLOCK to ALLOC_NOLOCK too?