From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1E044CD5BDE for ; Wed, 27 May 2026 09:11:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6283010E02C; Wed, 27 May 2026 09:11:38 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="dQ9+zHsT"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 09D9A10E02C; Wed, 27 May 2026 09:11:38 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 2C873600B0; Wed, 27 May 2026 09:11:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B3FBB1F000E9; Wed, 27 May 2026 09:11:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779873096; bh=w8SNyfroetexR/rsWgkA/TlWiipBp7W7BaOHpufW7us=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=dQ9+zHsTB5S8+cja+lPli2tAY5+rNntkB5VeiOTEpY+C+NfY++AcNcBmEyJ9mkNP+ Ss3skkru5b9Xx6jjSLC4Kak3xr6/+2TbdnHybyrf4PfNOx1C0zsF8CZRrNPy9h/GDr 055IOD7o0EWmIb9z2wC6R0m+GhluIF05AtDyKnDPGE5xqE6vjiu5NyVvsggY7ZOU+G sIMXNFpKI2wNq8hlxyEqT5iaTDPDanW5rm5WTeqddt3FExgugOtMakhdBcOhEI3ZaL 4XZPoFhBdJcblxf4qRrvuYgP4rJTYoE8SWlx3fY5xsZTm+Ed3cW4sWQbbdj5ne6V/B oYky6JCrszNZw== Message-ID: Date: Wed, 27 May 2026 11:11:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: improve the kmem_cache_alloc_bulk API Content-Language: en-US To: Christoph Hellwig , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Jesper Dangaard Brouer , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, io-uring@vger.kernel.org, kasan-dev@googlegroups.com, bpf@vger.kernel.org, netdev@vger.kernel.org References: <20260527070239.2252948-1-hch@lst.de> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 5/27/26 09:02, Christoph Hellwig wrote: > Hi all, > > kmem_cache_alloc_bulk has a very unintuitive and undocumented return > value convention. Fix that and add documentation. > > Note that the few comments explaining it mention that the gfp flags > must allow "spinning". That's not really a term used in the memory > allocator, is this supposed to mean "block" or "sleep"? Page allocator now has alloc_pages_nolock() for when no spinning is possible, and it uses ALLOC_TRYLOCK internally. Slab has kmalloc_nolock() relying on that when it needs new pages. In terms of gfp flags, such context is currently indicated by lack of __GFP_KSWAPD_RECLAIM, where lack of __GFP_DIRECT_RECLAIM only means "no sleeping" - see gfpflags_allow_spinning(). Slab uses it internally as there's no ALLOC_TRYLOCK, but also there are callers from memcg and stackdepot. Like the rest of gfp flags it's far from ideal, maybe we'll figure out a better design eventually. > Diffstat: > drivers/gpu/drm/msm/msm_iommu.c | 6 +-- > drivers/gpu/drm/panthor/panthor_mmu.c | 12 ++----- > include/linux/slab.h | 6 ++- > io_uring/io_uring.c | 23 +++++-------- > lib/test_meminit.c | 19 +++++------ > mm/kasan/kasan_test_c.c | 5 +- > mm/kfence/kfence_test.c | 9 ++--- > mm/slub.c | 58 ++++++++++++++++++---------------- > net/bpf/test_run.c | 7 +--- > net/core/skbuff.c | 23 +++++++------ > tools/include/linux/slab.h | 2 - > tools/testing/shared/linux.c | 19 ++++------- > 12 files changed, 92 insertions(+), 97 deletions(-)