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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 C2D5BC9833A for ; Sat, 26 Sep 2026 09:24:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=sTQndXxkIuwWKoVUm7RH0Lfp0eOzvHI6CoK2okedbuw=; b=pREm/dK9L4zuUyFOYyCqL/5Ii7 WDfAuH8MVu3+6qp53Y19yshu0EwcXsfB74ceOeS0NG9Hk7rygKVWULa8nSg476pq/xC+9lh11/L8m neiBWesoytxO95b+zEbGF94jzhY3L0gvkIMrcPNISrBdcfSthPVLQePjNHk6YkFLSFuVRpzfaedEO mhCEVcBgOjcK6pAoJe4qCAXYOhEi0MJtw4yyONwidIRIYXddbKfs3k66AmvZpT372Gpyqh7itOo4U UPFK0NV6qqXmFj6/JQ8sZcMasuaJ9jtvb/NacyogQMVouIN62H9R5A7EVWebBFkRMQj1zG3QNYf0/ k0ft2aiQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xAOeP-0000000FCdR-3YVm; Sat, 26 Sep 2026 09:24:57 +0000 Received: from mail-ed1-x548.google.com ([2a00:1450:4864:20::548]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xAOeN-0000000FCcQ-0yqY for kexec@lists.infradead.org; Sat, 26 Sep 2026 09:24:56 +0000 Received: by mail-ed1-x548.google.com with SMTP id 4fb4d7f45d1cf-6a5d57a8d51so2020622a12.1 for ; Sat, 26 Sep 2026 02:24:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790414693; x=1791019493; darn=lists.infradead.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=sTQndXxkIuwWKoVUm7RH0Lfp0eOzvHI6CoK2okedbuw=; b=UycT2wHasGtSlWbpcH+02qFpWLw8EwdJeqD6fPPfpWjz+MukMJfSVOXzPwuG5K7GzK 6W1GQme+w0vgtqe9u1mTaovZi2v2UswUnTbkSL3flkLCgEo/XoCXr4Sig05b5cJBMZxS s7xlOGIFvzg5kSlkRQPlRc8Qn5nCAUMVpjqtp4A7PcgynK8/R6dnVD/aoyrtdYmbKzvQ CCA+l1MafL/piyKv53Fo3EK1bmsnV/cAs23zOvaKVgDJo/5+I15B7khTZgelWVTeAfbr JRNY7CqTN/P6H4Wb1jKlIL0gFylPYn759hrlDyE6PaNH8iFdArDOASrWUB6SeQ57PZCn djaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790414693; x=1791019493; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=sTQndXxkIuwWKoVUm7RH0Lfp0eOzvHI6CoK2okedbuw=; b=i/FobRHJJSDfc/C2mb8v/u5kU2OhgTd92CwhwEo/V+wiOpfuyQ+Dm6EAdRuPxIUVpy s4CH/YjiHolwG4/su26Lhx0bldS2omYV06f7UQEHcb95EPVHHh+DkQT9VXGJvp/TouMh 1b4OC2vUe/VZ3mN3PYS+Ys4Q1+RzGfFbbGClzmx9gjZfBElwKI5UhNSKNZvV42yNaeJR dbEdy71qg01PxgojHji7AAJYjranR+YkVjpu0CvFDdzHpNg7fd63gCX610tnQp0s29qs 9QccNXHgMj3jdto42UCOD54edSRFiqDTMtWIObuTNqW4e7ormp7L/lPxx7+Z9A+POlae Le1A== X-Forwarded-Encrypted: i=1; AKwUvBxadlYl9M3bSPVoEnvTR/+mjtFPyOIZU296gvFU78Rk1NRYZ3fLsy0ucezoMRHUq75JmL6LGw==@lists.infradead.org X-Gm-Message-State: AFuF++n2Wra87IhkDmGyKCgH7rCgZhIBFbkPp1Zkwlexhd6AK+/I47ie +UJJr3htHbZq6SaotucTx5SzGaS/EbvwZwHDNO9Wb/fcNsNsISvq5iXhavY94iRhtVzVUxfE/vi YWqhin50R0pWWgNGKyw== X-Received: from edbet5.prod.google.com ([2002:a05:6402:3785:b0:6ab:222:1e7f]) (user=tarunsahu job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:23c7:b0:6a9:e7eb:f52f with SMTP id 4fb4d7f45d1cf-6aac90a9049mr5754388a12.28.1790414692533; Sat, 26 Sep 2026 02:24:52 -0700 (PDT) Date: Sat, 26 Sep 2026 09:24:48 +0000 In-Reply-To: <20260926092448.4090401-1-tarunsahu@google.com> Mime-Version: 1.0 References: <20260926092448.4090401-1-tarunsahu@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260926092448.4090401-2-tarunsahu@google.com> Subject: [PATCH v3 2/2] memblock: use binary search to locate candidate regions From: Tarun Sahu To: Andrew Morton , Pasha Tatashin , dmatlack@google.com, Mike Rapoport , kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org, dev.jain@arm.com, Pratyush Yadav , linux-mm@kvack.org, Tarun Sahu Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260926_022455_290589_79AE5E15 X-CRM114-Status: GOOD ( 15.34 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org Use binary search (memblock_bsearch_start) in memblock_add_range() and memblock_isolate_range() to locate candidate regions instead of linearly scanning from index 0. Under heavy memory fragmentation (such as KHO page preservation registering hundreds of thousands of disjoint folios), scanning from index 0 on every insertion and isolation results in O(N^2) complexity, causing boot-time memory retrieval to take several minutes (~268s for 393k pages). Using binary search reduces the worst-case complexity to O(N log N) (and O(N) for sequential appends), cutting KHO memory retrieval time from ~268s to ~50ms. memblock_search() open codes the same binary search, so reimplement it on top of the new helper. Signed-off-by: Tarun Sahu mm/memblock.c | 53 +++++++++++++++++++++++++++++++++++---------------- 1 file changed, 37 insertions(+), 16 deletions(-) diff --git a/mm/memblock.c b/mm/memblock.c index 59dda7d085f3..87c71435c80c 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -586,6 +586,33 @@ static void __init_memblock memblock_insert_region(struct memblock_type *type, type->total_size += size; } +/** + * memblock_bsearch_start - Find the first region index where rend > base + * @type: memblock type to search + * @base: base physical address of the candidate range + * + * Returns the first region index that could potentially overlap @base. + */ +static int __init_memblock memblock_bsearch_start(struct memblock_type *type, + phys_addr_t base) +{ + int mid, low = 0; + int high = type->cnt; + + if (type->cnt && base >= type->regions[type->cnt - 1].base + + type->regions[type->cnt - 1].size) + return type->cnt; + + while (low < high) { + mid = (low + high) / 2; + if (type->regions[mid].base + type->regions[mid].size <= base) + low = mid + 1; + else + high = mid; + } + return low; +} + /** * memblock_add_range - add new memblock region * @type: memblock type to add new region into @@ -609,7 +636,7 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, bool insert = false; phys_addr_t obase = base; phys_addr_t end = base + memblock_cap_size(base, &size); - int idx, nr_new, start_rgn = -1, end_rgn; + int idx, start_idx, nr_new, start_rgn = -1, end_rgn; if (!size) return 0; @@ -644,8 +671,9 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, */ base = obase; nr_new = 0; + start_idx = memblock_bsearch_start(type, base); - for (idx = 0; idx < type->cnt; idx++) { + for (idx = start_idx; idx < type->cnt; idx++) { struct memblock_region *rgn = &type->regions[idx]; phys_addr_t rbase = rgn->base; phys_addr_t rend = rbase + rgn->size; @@ -809,7 +837,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type, int *start_rgn, int *end_rgn) { phys_addr_t end = base + memblock_cap_size(base, &size); - int idx; + int idx, start_idx; *start_rgn = *end_rgn = 0; @@ -821,7 +849,9 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type, if (memblock_double_array(type, base, size) < 0) return -ENOMEM; - for (idx = 0; idx < type->cnt; idx++) { + start_idx = memblock_bsearch_start(type, base); + + for (idx = start_idx; idx < type->cnt; idx++) { struct memblock_region *rgn = &type->regions[idx]; phys_addr_t rbase = rgn->base; phys_addr_t rend = rbase + rgn->size; @@ -2062,19 +2092,10 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit) static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr) { - unsigned int left = 0, right = type->cnt; + int idx = memblock_bsearch_start(type, addr); - do { - unsigned int mid = (right + left) / 2; - - if (addr < type->regions[mid].base) - right = mid; - else if (addr >= (type->regions[mid].base + - type->regions[mid].size)) - left = mid + 1; - else - return mid; - } while (left < right); + if (idx < type->cnt && addr >= type->regions[idx].base) + return idx; return -1; } base-commit: 1f18d740165163910df64d3063e1ad31648bc5e0 -- 2.56.0.rc1.315.gc6ed9934b7-goog