From patchwork Fri Sep 2 21:10:50 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 12964671 X-Patchwork-Delegate: bpf@iogearbox.net 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A00CECAAA1 for ; Fri, 2 Sep 2022 21:11:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230488AbiIBVLe (ORCPT ); Fri, 2 Sep 2022 17:11:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229649AbiIBVLd (ORCPT ); Fri, 2 Sep 2022 17:11:33 -0400 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73182D91C9 for ; Fri, 2 Sep 2022 14:11:32 -0700 (PDT) Received: by mail-pj1-x102b.google.com with SMTP id l5so3112879pjy.5 for ; Fri, 02 Sep 2022 14:11:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=stV/ngTHq+LHFGpY9e6rDntSPSEwS4lPScETgTMBjXo=; b=iGbP92S7AoYyStgAIFscdU0byHZ4R4yfihu/ejpdEKBhGPmlXpbGDWKnOzFhw2y+iC R/4R/7mTdU9RRJqW7tEvn94oZDXiJx7wgbQ+yg4+ZBRNyAvo07qxit9ohqCQwOBMQClM q8FqOyD93ZPSg+4ZjcieqH9g9vER8W/svk+ruDhFwxgHLLJVbuPosJUFD8YEhzKOhrc9 RbZMxx2ShWpS/k8jcyJEF6Najg/RmmHtMw2Fjw81sjxq5uCsWb4HuFSJ4BIyNGq79qs0 2r1Hn9r29DPb86IbmNkp8EbJk6s+K2lsxdZ2leThfE4j4UgHauqVUPctfExp6vhmoy4F mSoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=stV/ngTHq+LHFGpY9e6rDntSPSEwS4lPScETgTMBjXo=; b=5b01ce8OkLpFjjBwaGWa5Age3YvRMm3Sd/w3ZTawT79bG52hHAr++XawcqAJEk0nan 6VoShmvE5jhL8sxx2PqEUVejt861ZlRlI7KHUi7eRlxrgt1KEfyGyXlRgo65o0VqABY5 lurPibDk/SCWkJmKIHCCbfeDCW0OcZ4ObgFDFZupgroqLj8AUQceC/Co1feY9MEgHmQf id1eICG9TNZWkXBAfEzcwcBh/YNQs2itoDMzbvlrmnkXBTnNj9q+bmX4eRvX5cooTtxa PbTvJhfHXNj27suWPkGTpi+KAxfqGNfdzLP1srgJW00V0xv0H/RduzHsqpX/hZbrq/7k tFqA== X-Gm-Message-State: ACgBeo1zrtWynYGq3K96tY6vSo0Ueg65LWgyH04omE/iBALX1cePeGQ9 xLUEtm2EenueXlKndgmOEYc= X-Google-Smtp-Source: AA6agR5n4FqfTJeMOgvOKydw7BaA2vMkvHK4qGfZi6dVup6svxdDjqrb+6/ZOPQBvzzINvJgxT3JeA== X-Received: by 2002:a17:90b:4c8d:b0:1f5:409b:b017 with SMTP id my13-20020a17090b4c8d00b001f5409bb017mr6991818pjb.52.1662153091882; Fri, 02 Sep 2022 14:11:31 -0700 (PDT) Received: from localhost.localdomain ([2620:10d:c090:500::c978]) by smtp.gmail.com with ESMTPSA id ik18-20020a170902ab1200b0017534ffd491sm2093987plb.163.2022.09.02.14.11.30 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 02 Sep 2022 14:11:31 -0700 (PDT) From: Alexei Starovoitov To: davem@davemloft.net Cc: daniel@iogearbox.net, andrii@kernel.org, tj@kernel.org, memxor@gmail.com, delyank@fb.com, linux-mm@kvack.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v6 bpf-next 08/16] bpf: Adjust low/high watermarks in bpf_mem_cache Date: Fri, 2 Sep 2022 14:10:50 -0700 Message-Id: <20220902211058.60789-9-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220902211058.60789-1-alexei.starovoitov@gmail.com> References: <20220902211058.60789-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Alexei Starovoitov The same low/high watermarks for every bucket in bpf_mem_cache consume significant amount of memory. Preallocating 64 elements of 4096 bytes each in the free list is not efficient. Make low/high watermarks and batching value dependent on element size. This change brings significant memory savings. Acked-by: Kumar Kartikeya Dwivedi Acked-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov --- kernel/bpf/memalloc.c | 50 +++++++++++++++++++++++++++++++------------ 1 file changed, 36 insertions(+), 14 deletions(-) diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index da0721f8c28f..7e5df6866d92 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -100,6 +100,7 @@ struct bpf_mem_cache { int unit_size; /* count of objects in free_llist */ int free_cnt; + int low_watermark, high_watermark, batch; }; struct bpf_mem_caches { @@ -118,14 +119,6 @@ static struct llist_node notrace *__llist_del_first(struct llist_head *head) return entry; } -#define BATCH 48 -#define LOW_WATERMARK 32 -#define HIGH_WATERMARK 96 -/* Assuming the average number of elements per bucket is 64, when all buckets - * are used the total memory will be: 64*16*32 + 64*32*32 + 64*64*32 + ... + - * 64*4096*32 ~ 20Mbyte - */ - static void *__alloc(struct bpf_mem_cache *c, int node) { /* Allocate, but don't deplete atomic reserves that typical @@ -220,7 +213,7 @@ static void free_bulk(struct bpf_mem_cache *c) if (IS_ENABLED(CONFIG_PREEMPT_RT)) local_irq_restore(flags); free_one(c, llnode); - } while (cnt > (HIGH_WATERMARK + LOW_WATERMARK) / 2); + } while (cnt > (c->high_watermark + c->low_watermark) / 2); /* and drain free_llist_extra */ llist_for_each_safe(llnode, t, llist_del_all(&c->free_llist_extra)) @@ -234,12 +227,12 @@ static void bpf_mem_refill(struct irq_work *work) /* Racy access to free_cnt. It doesn't need to be 100% accurate */ cnt = c->free_cnt; - if (cnt < LOW_WATERMARK) + if (cnt < c->low_watermark) /* irq_work runs on this cpu and kmalloc will allocate * from the current numa node which is what we want here. */ - alloc_bulk(c, BATCH, NUMA_NO_NODE); - else if (cnt > HIGH_WATERMARK) + alloc_bulk(c, c->batch, NUMA_NO_NODE); + else if (cnt > c->high_watermark) free_bulk(c); } @@ -248,9 +241,38 @@ static void notrace irq_work_raise(struct bpf_mem_cache *c) irq_work_queue(&c->refill_work); } +/* For typical bpf map case that uses bpf_mem_cache_alloc and single bucket + * the freelist cache will be elem_size * 64 (or less) on each cpu. + * + * For bpf programs that don't have statically known allocation sizes and + * assuming (low_mark + high_mark) / 2 as an average number of elements per + * bucket and all buckets are used the total amount of memory in freelists + * on each cpu will be: + * 64*16 + 64*32 + 64*64 + 64*96 + 64*128 + 64*196 + 64*256 + 32*512 + 16*1024 + 8*2048 + 4*4096 + * == ~ 116 Kbyte using below heuristic. + * Initialized, but unused bpf allocator (not bpf map specific one) will + * consume ~ 11 Kbyte per cpu. + * Typical case will be between 11K and 116K closer to 11K. + * bpf progs can and should share bpf_mem_cache when possible. + */ + static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu) { init_irq_work(&c->refill_work, bpf_mem_refill); + if (c->unit_size <= 256) { + c->low_watermark = 32; + c->high_watermark = 96; + } else { + /* When page_size == 4k, order-0 cache will have low_mark == 2 + * and high_mark == 6 with batch alloc of 3 individual pages at + * a time. + * 8k allocs and above low == 1, high == 3, batch == 1. + */ + c->low_watermark = max(32 * 256 / c->unit_size, 1); + c->high_watermark = max(96 * 256 / c->unit_size, 3); + } + c->batch = max((c->high_watermark - c->low_watermark) / 4 * 3, 1); + /* To avoid consuming memory assume that 1st run of bpf * prog won't be doing more than 4 map_update_elem from * irq disabled region @@ -392,7 +414,7 @@ static void notrace *unit_alloc(struct bpf_mem_cache *c) WARN_ON(cnt < 0); - if (cnt < LOW_WATERMARK) + if (cnt < c->low_watermark) irq_work_raise(c); return llnode; } @@ -425,7 +447,7 @@ static void notrace unit_free(struct bpf_mem_cache *c, void *ptr) local_dec(&c->active); local_irq_restore(flags); - if (cnt > HIGH_WATERMARK) + if (cnt > c->high_watermark) /* free few objects from current cpu into global kmalloc pool */ irq_work_raise(c); }