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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 322D1D62602 for ; Fri, 23 Jan 2026 06:53:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5CC2A6B040C; Fri, 23 Jan 2026 01:53:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 51E4F6B040E; Fri, 23 Jan 2026 01:53:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 38D296B040F; Fri, 23 Jan 2026 01:53:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 1E5116B040C for ; Fri, 23 Jan 2026 01:53:51 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D604216036F for ; Fri, 23 Jan 2026 06:53:50 +0000 (UTC) X-FDA: 84362313420.08.7D3E302 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf09.hostedemail.com (Postfix) with ESMTP id A4DA8140005 for ; Fri, 23 Jan 2026 06:53:48 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="Z2g9m/rc"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="u/P/pwZ9"; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="Z2g9m/rc"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="u/P/pwZ9"; dmarc=none; spf=pass (imf09.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769151228; h=from:from:sender: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:dkim-signature; bh=Lz6+CfboTVUMod3u7B664uLDJDmXudIqpgLE6OkuCxw=; b=Dmf5C9ltgf9/RfUFuJ/pJZccfzzNPkVKfL1V366RiKCjk00IE2PO0DyIgS/uyB0Zc6TXf0 EE3ZMvGKL1L6we8mVqQdoal4p0IvBg9ezLKXJXzMemXZ1nbcp32oQFcNJNNSSEjwiFvvq2 D6svEdCa6nLoZPyhvW3i8XZuLti3EuY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769151228; a=rsa-sha256; cv=none; b=7LxcacdxgOOkNZzTSr8wHE+PhEhwa+fSXUkmNg2ocEZNxKxRJg/LfVn4NtbMKLVtoyEdV8 X7Q+dIZEeVRA4I8HXJFboxUnJIm9y7PbhsMsAQn2fo/LnkdnTBrryImSJbjp6/WiMEZXJV f5/clH8SBihKcIAwq6d+9+HpBdIMXsY= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="Z2g9m/rc"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="u/P/pwZ9"; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="Z2g9m/rc"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="u/P/pwZ9"; dmarc=none; spf=pass (imf09.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id C9F8033772; Fri, 23 Jan 2026 06:53:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1769151190; h=from:from:reply-to: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=Lz6+CfboTVUMod3u7B664uLDJDmXudIqpgLE6OkuCxw=; b=Z2g9m/rcdQXb7ha3+S6UqASNZmOJNr7F30VJDOieU1AGvt+srX1olSuMb2LtLW0vnUEl2Y ZN/48UbRACPGgqHBdyew5JdSytha46m9hSDac//pLlIjia4RBo7098CZXcXccCRpXHDP7G Vypc5k7Lzp7SYcx4wPLpp+7Ndn5klNk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1769151190; h=from:from:reply-to: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=Lz6+CfboTVUMod3u7B664uLDJDmXudIqpgLE6OkuCxw=; b=u/P/pwZ9ky+Ip6KENw9mi4Y3FkSM4RJB211LC5waIXA/I+Q4De3PBR+9IK/NaIAqDCm8GB LJOLnePCSyAPYgCw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1769151190; h=from:from:reply-to: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=Lz6+CfboTVUMod3u7B664uLDJDmXudIqpgLE6OkuCxw=; b=Z2g9m/rcdQXb7ha3+S6UqASNZmOJNr7F30VJDOieU1AGvt+srX1olSuMb2LtLW0vnUEl2Y ZN/48UbRACPGgqHBdyew5JdSytha46m9hSDac//pLlIjia4RBo7098CZXcXccCRpXHDP7G Vypc5k7Lzp7SYcx4wPLpp+7Ndn5klNk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1769151190; h=from:from:reply-to: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=Lz6+CfboTVUMod3u7B664uLDJDmXudIqpgLE6OkuCxw=; b=u/P/pwZ9ky+Ip6KENw9mi4Y3FkSM4RJB211LC5waIXA/I+Q4De3PBR+9IK/NaIAqDCm8GB LJOLnePCSyAPYgCw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 7C249139F7; Fri, 23 Jan 2026 06:53:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2McKHtYac2k4YgAAD6G6ig (envelope-from ); Fri, 23 Jan 2026 06:53:10 +0000 From: Vlastimil Babka Date: Fri, 23 Jan 2026 07:52:51 +0100 Subject: [PATCH v4 13/22] slab: remove the do_slab_free() fastpath MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260123-sheaves-for-all-v4-13-041323d506f7@suse.cz> References: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> In-Reply-To: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> To: Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin Cc: Hao Li , Andrew Morton , Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , Sebastian Andrzej Siewior , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com, Vlastimil Babka X-Mailer: b4 0.14.3 X-Rspamd-Queue-Id: A4DA8140005 X-Stat-Signature: r5g89dykopbcfd8f84e53zzjg87h53ec X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769151228-45005 X-HE-Meta: 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 eNFiA6Yf IbWDGBSigJYbV0gEB0E5YFivuML+zgU8MCT7gWaYlVYl2ZnuQFxRK4l9wJYYFfcpY2aYLzc7DKLAvEaU6JlMSwGKvT1olCgfGgK0vBURU1P2iGL6psdyMhnucrM/OZACvtejMHnpZatxZRQhU/ABC+Y41eVWvXeuzqaNyUpk/FmsxxISiGX4SrtnAPH6z3IQj0fCTxrdw81IrC3ENvMYGIknYUhIf0ncrwSnAlM/swJaDGnwyzRvHJX2Ewy8BAUDo3dWB5Gjppbm+xAtR8J8Mn0dvbZkKpaVb+m3tXoJQWaMVuvnsWLrah3Gb9wi40IlS9NT9qip2ebfTKaiSyhnKC00QMy/Acd4xTGNo X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: We have removed cpu slab usage from allocation paths. Now remove do_slab_free() which was freeing objects to the cpu slab when the object belonged to it. Instead call __slab_free() directly, which was previously the fallback. This simplifies kfree_nolock() - when freeing to percpu sheaf fails, we can call defer_free() directly. Also remove functions that became unused. Reviewed-by: Harry Yoo Reviewed-by: Hao Li Reviewed-by: Suren Baghdasaryan Signed-off-by: Vlastimil Babka --- mm/slub.c | 149 ++++++-------------------------------------------------------- 1 file changed, 13 insertions(+), 136 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 914b51aedb25..a63a0eed2c55 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3678,29 +3678,6 @@ static inline unsigned int init_tid(int cpu) return cpu; } -static inline void note_cmpxchg_failure(const char *n, - const struct kmem_cache *s, unsigned long tid) -{ -#ifdef SLUB_DEBUG_CMPXCHG - unsigned long actual_tid = __this_cpu_read(s->cpu_slab->tid); - - pr_info("%s %s: cmpxchg redo ", n, s->name); - - if (IS_ENABLED(CONFIG_PREEMPTION) && - tid_to_cpu(tid) != tid_to_cpu(actual_tid)) { - pr_warn("due to cpu change %d -> %d\n", - tid_to_cpu(tid), tid_to_cpu(actual_tid)); - } else if (tid_to_event(tid) != tid_to_event(actual_tid)) { - pr_warn("due to cpu running other code. Event %ld->%ld\n", - tid_to_event(tid), tid_to_event(actual_tid)); - } else { - pr_warn("for unknown reason: actual=%lx was=%lx target=%lx\n", - actual_tid, tid, next_tid(tid)); - } -#endif - stat(s, CMPXCHG_DOUBLE_CPU_FAIL); -} - static void init_kmem_cache_cpus(struct kmem_cache *s) { #ifdef CONFIG_PREEMPT_RT @@ -4239,18 +4216,6 @@ static inline bool pfmemalloc_match(struct slab *slab, gfp_t gfpflags) return true; } -static inline bool -__update_cpu_freelist_fast(struct kmem_cache *s, - void *freelist_old, void *freelist_new, - unsigned long tid) -{ - struct freelist_tid old = { .freelist = freelist_old, .tid = tid }; - struct freelist_tid new = { .freelist = freelist_new, .tid = next_tid(tid) }; - - return this_cpu_try_cmpxchg_freelist(s->cpu_slab->freelist_tid, - &old.freelist_tid, new.freelist_tid); -} - /* * Get the slab's freelist and do not freeze it. * @@ -6185,99 +6150,6 @@ void defer_free_barrier(void) irq_work_sync(&per_cpu_ptr(&defer_free_objects, cpu)->work); } -/* - * Fastpath with forced inlining to produce a kfree and kmem_cache_free that - * can perform fastpath freeing without additional function calls. - * - * The fastpath is only possible if we are freeing to the current cpu slab - * of this processor. This typically the case if we have just allocated - * the item before. - * - * If fastpath is not possible then fall back to __slab_free where we deal - * with all sorts of special processing. - * - * Bulk free of a freelist with several objects (all pointing to the - * same slab) possible by specifying head and tail ptr, plus objects - * count (cnt). Bulk free indicated by tail pointer being set. - */ -static __always_inline void do_slab_free(struct kmem_cache *s, - struct slab *slab, void *head, void *tail, - int cnt, unsigned long addr) -{ - /* cnt == 0 signals that it's called from kfree_nolock() */ - bool allow_spin = cnt; - struct kmem_cache_cpu *c; - unsigned long tid; - void **freelist; - -redo: - /* - * Determine the currently cpus per cpu slab. - * The cpu may change afterward. However that does not matter since - * data is retrieved via this pointer. If we are on the same cpu - * during the cmpxchg then the free will succeed. - */ - c = raw_cpu_ptr(s->cpu_slab); - tid = READ_ONCE(c->tid); - - /* Same with comment on barrier() in __slab_alloc_node() */ - barrier(); - - if (unlikely(slab != c->slab)) { - if (unlikely(!allow_spin)) { - /* - * __slab_free() can locklessly cmpxchg16 into a slab, - * but then it might need to take spin_lock - * for further processing. - * Avoid the complexity and simply add to a deferred list. - */ - defer_free(s, head); - } else { - __slab_free(s, slab, head, tail, cnt, addr); - } - return; - } - - if (unlikely(!allow_spin)) { - if ((in_nmi() || !USE_LOCKLESS_FAST_PATH()) && - local_lock_is_locked(&s->cpu_slab->lock)) { - defer_free(s, head); - return; - } - cnt = 1; /* restore cnt. kfree_nolock() frees one object at a time */ - } - - if (USE_LOCKLESS_FAST_PATH()) { - freelist = READ_ONCE(c->freelist); - - set_freepointer(s, tail, freelist); - - if (unlikely(!__update_cpu_freelist_fast(s, freelist, head, tid))) { - note_cmpxchg_failure("slab_free", s, tid); - goto redo; - } - } else { - __maybe_unused unsigned long flags = 0; - - /* Update the free list under the local lock */ - local_lock_cpu_slab(s, flags); - c = this_cpu_ptr(s->cpu_slab); - if (unlikely(slab != c->slab)) { - local_unlock_cpu_slab(s, flags); - goto redo; - } - tid = c->tid; - freelist = c->freelist; - - set_freepointer(s, tail, freelist); - c->freelist = head; - c->tid = next_tid(tid); - - local_unlock_cpu_slab(s, flags); - } - stat_add(s, FREE_FASTPATH, cnt); -} - static __fastpath_inline void slab_free(struct kmem_cache *s, struct slab *slab, void *object, unsigned long addr) @@ -6294,7 +6166,7 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object, return; } - do_slab_free(s, slab, object, object, 1, addr); + __slab_free(s, slab, object, object, 1, addr); } #ifdef CONFIG_MEMCG @@ -6303,7 +6175,7 @@ static noinline void memcg_alloc_abort_single(struct kmem_cache *s, void *object) { if (likely(slab_free_hook(s, object, slab_want_init_on_free(s), false))) - do_slab_free(s, virt_to_slab(object), object, object, 1, _RET_IP_); + __slab_free(s, virt_to_slab(object), object, object, 1, _RET_IP_); } #endif @@ -6318,7 +6190,7 @@ void slab_free_bulk(struct kmem_cache *s, struct slab *slab, void *head, * to remove objects, whose reuse must be delayed. */ if (likely(slab_free_freelist_hook(s, &head, &tail, &cnt))) - do_slab_free(s, slab, head, tail, cnt, addr); + __slab_free(s, slab, head, tail, cnt, addr); } #ifdef CONFIG_SLUB_RCU_DEBUG @@ -6344,14 +6216,14 @@ static void slab_free_after_rcu_debug(struct rcu_head *rcu_head) /* resume freeing */ if (slab_free_hook(s, object, slab_want_init_on_free(s), true)) - do_slab_free(s, slab, object, object, 1, _THIS_IP_); + __slab_free(s, slab, object, object, 1, _THIS_IP_); } #endif /* CONFIG_SLUB_RCU_DEBUG */ #ifdef CONFIG_KASAN_GENERIC void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr) { - do_slab_free(cache, virt_to_slab(x), x, x, 1, addr); + __slab_free(cache, virt_to_slab(x), x, x, 1, addr); } #endif @@ -6557,7 +6429,12 @@ void kfree_nolock(const void *object) return; } - do_slab_free(s, slab, x, x, 0, _RET_IP_); + /* + * __slab_free() can locklessly cmpxchg16 into a slab, but then it might + * need to take spin_lock for further processing. + * Avoid the complexity and simply add to a deferred list. + */ + defer_free(s, x); } EXPORT_SYMBOL_GPL(kfree_nolock); @@ -6983,7 +6860,7 @@ static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p) if (kfence_free(df.freelist)) continue; - do_slab_free(df.s, df.slab, df.freelist, df.tail, df.cnt, + __slab_free(df.s, df.slab, df.freelist, df.tail, df.cnt, _RET_IP_); } while (likely(size)); } @@ -7069,7 +6946,7 @@ __refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min, cnt++; object = get_freepointer(s, object); } while (object); - do_slab_free(s, slab, head, tail, cnt, _RET_IP_); + __slab_free(s, slab, head, tail, cnt, _RET_IP_); } if (refilled >= max) -- 2.52.0