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 7E7C9CD6E44 for ; Thu, 28 May 2026 09:53:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B3FF6B0096; Thu, 28 May 2026 05:53:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 63DD16B0099; Thu, 28 May 2026 05:53:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 55B796B0096; Thu, 28 May 2026 05:53:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 40C5F6B0096 for ; Thu, 28 May 2026 05:53:23 -0400 (EDT) Received: from smtpin15.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 04B6CC279F for ; Thu, 28 May 2026 09:53:22 +0000 (UTC) X-FDA: 84816365886.15.FFF8444 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) by imf21.hostedemail.com (Postfix) with ESMTP id 75B441C0007 for ; Thu, 28 May 2026 09:53:21 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=MFvO0i0i; spf=pass (imf21.hostedemail.com: domain of hao.li@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=hao.li@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1779962001; a=rsa-sha256; cv=none; b=xt+0+a+JUVGYpteR21M5GJl5/1MfErCDEt5k+24uY5UUPycQzjTTbEMU3dF4W5lYQO4HnE IBp5Krs+HkILwDxgV79Gb7X9bc5Mawa06/Z+KdDPcVjoCqt5QAPNwdfTNdDb8gbmjAGzxU ZxnUO3P6hcg6sktsWtgL+ko52tuudEc= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=MFvO0i0i; spf=pass (imf21.hostedemail.com: domain of hao.li@linux.dev designates 91.218.175.170 as permitted sender) smtp.mailfrom=hao.li@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1779962001; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7Psi/3PdGYQ/8BNVb4Dult2mh9IIeWs6X+I0h1Ys+4s=; b=ICnFGQsIeanWRUmztT3XRh3apKBPxkp3yTqAhFnZAPvx39G2ACRYPRfmqWXlshVNeH2PLa X/ByBXqCvyseVopysHkr7wI4KIh97nEnGePCVhruk736yDGEJbYioiUx3d7ijTrm7OJ2/x lkhMRB2rdtpn0EZOh1Dwd4BKUeVrsxg= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779961999; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7Psi/3PdGYQ/8BNVb4Dult2mh9IIeWs6X+I0h1Ys+4s=; b=MFvO0i0i8oD03Zk4F4oBxnrdZN92TFSlALnlmqAM2vtQEzVA/wIphM7iFUXo3AGL8DX/Vi oYoArEu82HTsvhp+EMKbRJruB5IbtLZecAJQLrvYDbLL6gedfg7haDTjsHd2AJRxmaiBQh iNwwye44gXCxTXcYHgku4EhHyCkwOyg= From: Hao Li To: vbabka@kernel.org, harry@kernel.org, akpm@linux-foundation.org Cc: cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Li Subject: [PATCH v2 1/2] mm/slub: detach and reattach partial slabs in batch Date: Thu, 28 May 2026 17:52:43 +0800 Message-ID: <20260528095254.43721-2-hao.li@linux.dev> In-Reply-To: <20260528095254.43721-1-hao.li@linux.dev> References: <20260528095254.43721-1-hao.li@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 75B441C0007 X-Stat-Signature: gu4cbom4imiii3545bqz3chyhczhegff X-HE-Tag: 1779962001-560939 X-HE-Meta: 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 0vTq4uyW jRTQVTQ1TwD0zYP2pZY2taI+uyK4kqsTP7EykLGlOF7bJbvfY/3I0ZydLh3y+pNr389dERW5x5ZTnv+PCGEDJrr7KZG9iUn19Lgr18f72pCRmVUHgK8dKZJWTHd3HGKrZOtYHE7zsvyhDyu7C1Njro1bcJRbbrvhDSq6Mq0mkpnRyS2c/R4qZXs3ElP8gJMzOCi6z Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: get_partial_node_bulk() moves each selected slab from the node's partial list to the local pc->slabs list using a remove_partial() and list_add() pair. In practice, the loop often detaches several adjacent slabs. Doing this individually repeatedly manipulates list pointers while holding n->list_lock, which causes unnecessary churn. To demonstrate this, the counts below show how often single vs. multiple consecutive slabs are retrieved during a will-it-scale mmap stress test: consecutive_slabs_count frequency = 1 277345324 = 2 335238023 = 3 175717884 >= 4 88862337 The data confirms that retrieving multiple contiguous slabs is highly frequent. To optimize this, track contiguous runs of matching slabs and move each run in a single operation using list_bulk_move_tail(). This reduces list pointer churn inside the lock critical section. Apply the same optimization to __refill_objects_node() when reattaching leftover partial slabs back to the node's partial list. The will-it-scale mmap benchmark shows a 2% ~ 5% performance improvement after applying this patch. Signed-off-by: Hao Li --- mm/slub.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index b9f10b869914..eb60b3da23ff 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3739,6 +3739,7 @@ static bool get_partial_node_bulk(struct kmem_cache *s, bool allow_spin) { struct slab *slab, *slab2; + struct slab *first = NULL, *last = NULL; unsigned int total_free = 0; unsigned long flags; @@ -3757,8 +3758,15 @@ static bool get_partial_node_bulk(struct kmem_cache *s, struct freelist_counters flc; unsigned int slab_free; - if (!pfmemalloc_match(slab, pc->flags)) + if (!pfmemalloc_match(slab, pc->flags)) { + if (first) { + list_bulk_move_tail(&pc->slabs, + &first->slab_list, + &last->slab_list); + first = NULL; + } continue; + } /* * determine the number of free objects in the slab racily @@ -3775,15 +3783,21 @@ static bool get_partial_node_bulk(struct kmem_cache *s, && total_free + slab_free > pc->max_objects) break; - remove_partial(n, slab); - - list_add(&slab->slab_list, &pc->slabs); + if (!first) + first = slab; + last = slab; + slab_clear_node_partial(slab); + n->nr_partial--; total_free += slab_free; if (total_free >= pc->max_objects) break; } + if (first) + list_bulk_move_tail(&pc->slabs, &first->slab_list, + &last->slab_list); + spin_unlock_irqrestore(&n->list_lock, flags); return total_free > 0; } @@ -7194,12 +7208,13 @@ __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int mi if (!list_empty(&pc.slabs)) { spin_lock_irqsave(&n->list_lock, flags); - list_for_each_entry_safe(slab, slab2, &pc.slabs, slab_list) { - - list_del(&slab->slab_list); - add_partial(n, slab, ADD_TO_TAIL); + list_for_each_entry(slab, &pc.slabs, slab_list) { + slab_set_node_partial(slab); + n->nr_partial++; } + list_splice_tail(&pc.slabs, &n->partial); + spin_unlock_irqrestore(&n->list_lock, flags); } -- 2.54.0