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GET /api/1.1/patches/2221810/?format=api
{ "id": 2221810, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2221810/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260410120318.525653921@kernel.org/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/1.1/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/" }, "msgid": "<20260410120318.525653921@kernel.org>", "date": "2026-04-10T12:19:37", "name": "[14/38] slub: Use prandom instead of get_cycles()", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "d76d96b82f60f87a8f31119e8bc4a0b5643c2467", "submitter": { "id": 92397, "url": "http://patchwork.ozlabs.org/api/1.1/people/92397/?format=api", "name": "Thomas Gleixner", "email": "tglx@kernel.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260410120318.525653921@kernel.org/mbox/", "series": [ { "id": 499449, "url": "http://patchwork.ozlabs.org/api/1.1/series/499449/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=499449", "date": "2026-04-10T12:18:27", "name": "treewide: Cleanup LATCH, CLOCK_TICK_RATE and get_cycles() [ab]use", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/499449/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2221810/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2221810/checks/", "tags": {}, "headers": { "Return-Path": "\n <linuxppc-dev+bounces-19584-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linuxppc-dev@lists.ozlabs.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=t3jBR9hr;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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Fri, 10 Apr 2026 22:19:42 +1000 (AEST)", "from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58])\n\tby sea.source.kernel.org (Postfix) with ESMTP id B87CF44580;\n\tFri, 10 Apr 2026 12:19:40 +0000 (UTC)", "by smtp.kernel.org (Postfix) with ESMTPSA id 6F0FAC19421;\n\tFri, 10 Apr 2026 12:19:39 +0000 (UTC)" ], "ARC-Seal": "i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1775823583;\n\tcv=none;\n b=e7qM008jkRGS7xy0dEcB/Qot3l7Cn1kKs5CEZKcJtBL+81ucdJVdNFAvPBBtTqvXFsQz9Evsi/iQpBtAU+YCNkXYYxpORe7QynfvTY5KUyt9E3bxdF2GGo9zCpGBpmoRysnfGIpFRiYKEOC92krqIH2EunAU5EI0Tz3w9m+lwu8TpVu8KYEJZWfu68bln5yLngtNDQRPFF4i6jPo0Uyb4pCn5LZ7wTLC2an4uS6t7cVVJ60MYoFSPpmO0U0ZnuY+BRwVgNwEv+xAPXFtBDEG2Jc9f4vgx5cZt7Z+73JaZcPJNeuF0VN5wg5it17yKVEaWc6VjEYFuFPG86ftfOGs9w==", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1775823583; c=relaxed/relaxed;\n\tbh=l/i7/xAykrEqhXZEt+AYWUOXkyMBaQ0jVLhvmI8QgSc=;\n\th=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version:\n\t Content-Type;\n b=fNGOFHUeKfZpXBau8f/GpkPoQTXqxTZznH3a5wm1PU58xMlh38FyylzEMvFulJE3hlUuLtthlmv9dAo3UPqDwG59QKwXKOJysiKcevok+1BMk+vZRG7d2wQCBhX7IJE+5aKkERkNCBwJqjWTAe32gosdviytHpR2Ox2ugyqgujUqsOe9YrYKH/gsSqkRVdaF6QRebnyvsmAwSXQk1aL0BdpWiRHsC+WsIPpCi0mncXgp73Q4d7+0CHRxDUJymoE4HBH7jo4w16wB3nN9ALwNxaps1MqcsPh3gH3Cv/Mr7wcPW5oRZdvo/ktSmVM50vryUiHBzSuiawmq1hlcgEepqQ==", "ARC-Authentication-Results": "i=1; lists.ozlabs.org;\n dmarc=pass (p=quarantine dis=none) header.from=kernel.org;\n dkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=t3jBR9hr; dkim-atps=neutral;\n spf=pass (client-ip=172.234.252.31; helo=sea.source.kernel.org;\n envelope-from=tglx@kernel.org;\n receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n\ts=k20201202; t=1775823580;\n\tbh=mpxbBHJF6rhzMhSEUiQvC99JYsoAEEbwdTduYzlxEPc=;\n\th=Date:From:To:Cc:Subject:References:From;\n\tb=t3jBR9hrloEPurMHDq+39Qmu/knh8sc4zRVE8/2evrp72m0jjf5ZLkiqhTfHJf3lQ\n\t UuLDw1roDamtB5PCEFrCj4Am/iqY2B6Eqxv0IhuFUbghxXFtjb45YYjGv/1iSpakD6\n\t TFwz04dexWQxc2lpHNkB6gue2paUp+SphQGzt3h2nfY78uDiPTzZOojY3e61FIsW5V\n\t nWhQqjnOO5JiF4o/mhmPEmcNABsipUeHkNa04EcUPJl0rFmYRv/1fqlaU1qeGqFkTx\n\t Wm9D7sRbThBkNSUjiYqRay+oEzZSBtooNF5Q5Yp17uiVAaos9NzjDw3gIyxmgs/heb\n\t T0VBqEkO+l/iw==", "Date": "Fri, 10 Apr 2026 14:19:37 +0200", "Message-ID": "<20260410120318.525653921@kernel.org>", "User-Agent": "quilt/0.68", "From": "Thomas Gleixner <tglx@kernel.org>", "To": "LKML <linux-kernel@vger.kernel.org>", "Cc": "Vlastimil Babka <vbabka@kernel.org>,\n linux-mm@kvack.org,\n Arnd Bergmann <arnd@arndb.de>,\n x86@kernel.org,\n Lu Baolu <baolu.lu@linux.intel.com>,\n iommu@lists.linux.dev,\n Michael Grzeschik <m.grzeschik@pengutronix.de>,\n netdev@vger.kernel.org,\n linux-wireless@vger.kernel.org,\n Herbert Xu <herbert@gondor.apana.org.au>,\n linux-crypto@vger.kernel.org,\n David Woodhouse <dwmw2@infradead.org>,\n Bernie Thompson <bernie@plugable.com>,\n linux-fbdev@vger.kernel.org,\n \"Theodore Tso\" <tytso@mit.edu>,\n linux-ext4@vger.kernel.org,\n Andrew Morton <akpm@linux-foundation.org>,\n Uladzislau Rezki <urezki@gmail.com>,\n Marco Elver <elver@google.com>,\n Dmitry Vyukov <dvyukov@google.com>,\n kasan-dev@googlegroups.com,\n Andrey Ryabinin <ryabinin.a.a@gmail.com>,\n Thomas Sailer <t.sailer@alumni.ethz.ch>,\n linux-hams@vger.kernel.org,\n \"Jason A. Donenfeld\" <Jason@zx2c4.com>,\n Richard Henderson <richard.henderson@linaro.org>,\n linux-alpha@vger.kernel.org,\n Russell King <linux@armlinux.org.uk>,\n linux-arm-kernel@lists.infradead.org,\n Catalin Marinas <catalin.marinas@arm.com>,\n Huacai Chen <chenhuacai@kernel.org>,\n loongarch@lists.linux.dev,\n Geert Uytterhoeven <geert@linux-m68k.org>,\n linux-m68k@lists.linux-m68k.org,\n Dinh Nguyen <dinguyen@kernel.org>,\n Jonas Bonn <jonas@southpole.se>,\n linux-openrisc@vger.kernel.org,\n Helge Deller <deller@gmx.de>,\n linux-parisc@vger.kernel.org,\n Michael Ellerman <mpe@ellerman.id.au>,\n linuxppc-dev@lists.ozlabs.org,\n Paul Walmsley <pjw@kernel.org>,\n linux-riscv@lists.infradead.org,\n Heiko Carstens <hca@linux.ibm.com>,\n linux-s390@vger.kernel.org,\n \"David S. Miller\" <davem@davemloft.net>,\n sparclinux@vger.kernel.org", "Subject": "[patch 14/38] slub: Use prandom instead of get_cycles()", "References": "<20260410120044.031381086@kernel.org>", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=UTF-8", "X-Spam-Status": "No, score=-0.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "The decision whether to scan remote nodes is based on a 'random' number\nretrieved via get_cycles(). get_cycles() is about to be removed.\n\nThere is already prandom state in the code, so use that instead.\n\nSigned-off-by: Thomas Gleixner <tglx@kernel.org>\nCc: Vlastimil Babka <vbabka@kernel.org>\nCc: linux-mm@kvack.org\n---\n mm/slub.c | 37 +++++++++++++++++++++++--------------\n 1 file changed, 23 insertions(+), 14 deletions(-)", "diff": "--- a/mm/slub.c\n+++ b/mm/slub.c\n@@ -3302,6 +3302,25 @@ static inline struct slab *alloc_slab_pa\n \treturn slab;\n }\n \n+#if defined(CONFIG_SLAB_FREELIST_RANDOM) || defined(CONFIG_NUMA)\n+static DEFINE_PER_CPU(struct rnd_state, slab_rnd_state);\n+\n+static unsigned int slab_get_prandom_state(unsigned int limit)\n+{\n+\tstruct rnd_state *state;\n+\tunsigned int res;\n+\n+\t/*\n+\t * An interrupt or NMI handler might interrupt and change\n+\t * the state in the middle, but that's safe.\n+\t */\n+\tstate = &get_cpu_var(slab_rnd_state);\n+\tres = prandom_u32_state(state) % limit;\n+\tput_cpu_var(slab_rnd_state);\n+\treturn res;\n+}\n+#endif\n+\n #ifdef CONFIG_SLAB_FREELIST_RANDOM\n /* Pre-initialize the random sequence cache */\n static int init_cache_random_seq(struct kmem_cache *s)\n@@ -3365,8 +3384,6 @@ static void *next_freelist_entry(struct\n \treturn (char *)start + idx;\n }\n \n-static DEFINE_PER_CPU(struct rnd_state, slab_rnd_state);\n-\n /* Shuffle the single linked freelist based on a random pre-computed sequence */\n static bool shuffle_freelist(struct kmem_cache *s, struct slab *slab,\n \t\t\t bool allow_spin)\n@@ -3383,15 +3400,7 @@ static bool shuffle_freelist(struct kmem\n \tif (allow_spin) {\n \t\tpos = get_random_u32_below(freelist_count);\n \t} else {\n-\t\tstruct rnd_state *state;\n-\n-\t\t/*\n-\t\t * An interrupt or NMI handler might interrupt and change\n-\t\t * the state in the middle, but that's safe.\n-\t\t */\n-\t\tstate = &get_cpu_var(slab_rnd_state);\n-\t\tpos = prandom_u32_state(state) % freelist_count;\n-\t\tput_cpu_var(slab_rnd_state);\n+\t\tpos = slab_get_prandom_state(freelist_count);\n \t}\n \n \tpage_limit = slab->objects * s->size;\n@@ -3882,7 +3891,7 @@ static void *get_from_any_partial(struct\n \t * with available objects.\n \t */\n \tif (!s->remote_node_defrag_ratio ||\n-\t\t\tget_cycles() % 1024 > s->remote_node_defrag_ratio)\n+\t slab_get_prandom_state(1024) > s->remote_node_defrag_ratio)\n \t\treturn NULL;\n \n \tdo {\n@@ -7102,7 +7111,7 @@ static unsigned int\n \n \t/* see get_from_any_partial() for the defrag ratio description */\n \tif (!s->remote_node_defrag_ratio ||\n-\t\t\tget_cycles() % 1024 > s->remote_node_defrag_ratio)\n+\t slab_get_prandom_state(1024) > s->remote_node_defrag_ratio)\n \t\treturn 0;\n \n \tdo {\n@@ -8421,7 +8430,7 @@ void __init kmem_cache_init_late(void)\n \tflushwq = alloc_workqueue(\"slub_flushwq\", WQ_MEM_RECLAIM | WQ_PERCPU,\n \t\t\t\t 0);\n \tWARN_ON(!flushwq);\n-#ifdef CONFIG_SLAB_FREELIST_RANDOM\n+#if defined(CONFIG_SLAB_FREELIST_RANDOM) || defined(CONFIG_NUMA)\n \tprandom_init_once(&slab_rnd_state);\n #endif\n }\n", "prefixes": [ "14/38" ] }