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 DAFA8C982D6 for ; Fri, 18 Sep 2026 00:22:50 +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=2457T8NXpe+VYhyIx4NQQZX9J7v7gQmMrsUW0L2lVQ0=; b=3CmCmgPJKYsBhOPqwX0feihDCO WFbvpes4YWwDqwccxi8H2mP8r4bQrTf6rZNAGWhp7AtkxIp0doMCv02CldT0hydj0aF+o10FYrU04 W2f7PQgiNkdc8vTvpL4037fHDiW5ytMspkEYoagTmOlqBf+YD6CB3ichxitp9LnV9ONk2LCNf3ajR WLnjUyhyiq4YGQbMbKl2uAgT3Pd1NiTvZpX+bGidiPniEU8WCELKlXBk1ftjQgcZh+qeTwoACDtxe rwpC4XfXYQ5KqJ9tQCCRF6L7koX4ufD+aEHdV3IG43MmV8mrsJUQXMUhLXWAeysZrnrSiXSl3gFnn g0DQmw9w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7MNL-0000000D199-48Hb; Fri, 18 Sep 2026 00:22:47 +0000 Received: from mail-ej1-x646.google.com ([2a00:1450:4864:20::646]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7MNJ-0000000D18J-15qO for kexec@lists.infradead.org; Fri, 18 Sep 2026 00:22:46 +0000 Received: by mail-ej1-x646.google.com with SMTP id a640c23a62f3a-c293743f5cdso22841466b.0 for ; Thu, 17 Sep 2026 17:22:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789690963; x=1790295763; 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=2457T8NXpe+VYhyIx4NQQZX9J7v7gQmMrsUW0L2lVQ0=; b=fh/Hl5yASNUcGPQQREF40a7ovMZIZIenlgT068EjAbwpqLXOl2oclF35IlsS+ywkhI Fj0UZTR8EW7VASqr/LtShC57hylH5mrpMlawoaMJ2RfSktzp0vZNlEUvFbY2WDeX/3Zx e+fxmxt1v6yFG7etKOO0vmz3fmZQ30A6lRhsqjg6B+nphrll59W+e27wNVRJMyPKmThf UDOf39IsXizNfMmKBFIgcTmR7+GrUOcqSssUdVTcOwU5/fyUiVOWQn3oUd9h2LS2lsve gchUP6hyw6qBUgzqLxMiiTwR7NYgvbR7fXikNNgNJ6Ufou4RSA2/TKZCED/U+5OW4aQZ LQKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789690963; x=1790295763; 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=2457T8NXpe+VYhyIx4NQQZX9J7v7gQmMrsUW0L2lVQ0=; b=XfCaLihooX6gTrHFxNHzoUdE/3zQ3X2wwkbkvezaUOUUnRElCRTkgAFzdfu5yoVJh8 gNrCz6HStnvRcWWoi0KZOEKhQL5GS09j+19SmH7+k5MstxFctfNWyT/0/P+ZkvwfGR44 8XDYPLb7QMD91a5Yaa43MgyNzJYnSRK6WJlS97fQUPMLGhVP/x3QpCkUOTPct+JmYzFl EkFFlNvfXIVb2Pr+2ybIJ5J7Z3+LmNifV8eGmULe6R9M/jV2dzcrorynuGNn7YkrSbeW XejjH8NmrwpyC3TyhUYD6IqNKYQODzXsbtExq8EdpaMZj6uWebpyWaMXYhvilVRrgeg5 sy3A== X-Forwarded-Encrypted: i=1; AKwUvBx3KiCzQ/eryfR05EPfSNJ4gSPTkC2A2TSJhZcuSKT+PhQZdqp6XqJYStpnJEVwQpcE26Q9Gw==@lists.infradead.org X-Gm-Message-State: AFuF++kqTfnU3gkaewFltr5NJuKgIXvaOnmGOaE/rNMtjjCW9U2sNdt4 1dugfx2XkBKvAJnn3Bqi8jt+fwAOwDMqPXFn/sV3YNO+RWxquvIXF/kdv99hKxYhVXaX+8u1YwG nSck8I+Dc9bsqh0QfIA== X-Received: from ejcgo34.prod.google.com ([2002:a17:907:da2:b0:c29:de6c:6ff9]) (user=tarunsahu job=prod-delivery.src-stubby-dispatcher) by 2002:a17:907:3c96:b0:c26:30fa:7cf2 with SMTP id a640c23a62f3a-c2a157fbe2fmr84040766b.13.1789690962738; Thu, 17 Sep 2026 17:22:42 -0700 (PDT) Date: Fri, 18 Sep 2026 00:22:39 +0000 In-Reply-To: <20260918002239.4024231-1-tarunsahu@google.com> Mime-Version: 1.0 References: <20260918002239.4024231-1-tarunsahu@google.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260918002239.4024231-2-tarunsahu@google.com> Subject: [PATCH v2 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-20260917_172245_334601_57FC008C X-CRM114-Status: GOOD ( 16.14 ) 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 5aae75d34dec..00a8768de988 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; struct memblock_region *rgn; if (!size) @@ -645,8 +672,9 @@ 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++) { rgn = &type->regions[idx]; phys_addr_t rbase = rgn->base; phys_addr_t rend = rbase + rgn->size; @@ -810,7 +838,7 @@ 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; struct memblock_region *rgn; *start_rgn = *end_rgn = 0; @@ -823,7 +851,9 @@ 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++) { rgn = &type->regions[idx]; phys_addr_t rbase = rgn->base; phys_addr_t rend = rbase + rgn->size; @@ -2064,19 +2094,10 @@ 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; } -- 2.55.0.1082.g2b9226bbc0-goog