From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9FC8C3A1D01 for ; Sat, 26 Sep 2026 09:24:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790414696; cv=none; b=j0NSwCKpA27TizhZv3iKT/+JscutSzGjaTaSv4F8opEg1UndgUvt1BGtHmnkmkTdQUK+urcecal6YU9hvdbSVlZ5oBtO/nY1cJo1BmU0UEyXr2AxNRSLVYNmsz3D4NQg2yrb4GEb+Lg14Dj1FvYMGUBySpyh7lyaQTR00I4UP10= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790414696; c=relaxed/simple; bh=SLihxkP9x8ol5wzb2ncH+ajiz1GnnwONL2S2uxqu5mQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FyRbuAe1Kpdn3HQXy40Bx4Toxj0KkDaaUU67sYPLJBy2Vqu5aXRd3V/xy8FNMrO9V08rMPR5zcOrF1xdCz3RYw2TbITNNFU48G7pH6kFEc3PWZIrCfeWsM5m36SsDYrg/9VZZEc6n50hC07HuCT7bFzjhhNNZnfY8FvMWttpn+M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--tarunsahu.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=BcvfdSZh; arc=none smtp.client-ip=209.85.208.72 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--tarunsahu.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="BcvfdSZh" Received: by mail-ed1-f72.google.com with SMTP id 4fb4d7f45d1cf-6a5d57a8d51so2020623a12.1 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=vger.kernel.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=BcvfdSZhuUcQ2KS/D9VSyPYNg3p9oRnfgYi58xIpFbbQT8r4NbEE82NqZJB6M1LY3v yuRe+pTmnBh3rXeLxLFIvFWMQSI2/r19SwMoWFnwKExlP6bUg1TW1LhaveSxoogz4/eZ HR+zwPHN30MQ4Tcd78GE4lSY4/9gw97ewWXYzVgChCwc+bx2oQ9iExoJnr8V/CtRkf8N 702UQe0c8vKE31nkOSt83hWvVnO2AMUuT0Yj1wevdjh82Eo9zufMZ5lI8/cJF44nFtRc tSiD9wGxU8OJynUw6JnfpdY78Dr0acUl/nFFh1qeUKUr539OJyeZc2HaVmlwBZ1mFtbU nLuQ== 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=OISrc5/3f8G5pLJQpe6eET83LzAhZA7j6bLqFw4be3fHeRaYgjiX7ak4BTyKJvl8Yb KxnEw9xsZvvcpNL7q1XZNf/xRyGfsfBc+8Wf8P9XOXSiz2S8C0Ln3zvD8BvlnpBvdeVa tIHV4PHTtc6f0lYQw3lXRYggXr0pi7FJnABSJVVCv86eMtOf/YliUFA1pMvGBr7dcCUy 7Lpy2T0ce3myHbc1RzkjBRsgUCX5HG1aciVqSoaaRyUUGhBf/2jOZ6Tw0A6ZZSvUYBly S4HsBUeuTTGe1fDKKhVdjBw+1Xh9mnKWmdyPDgp3uOR15T6xuWbLbjupTviOVfbB06bC 6BfA== X-Gm-Message-State: AFuF++nAAbT1fSo7oGR4LTPbLadMwUf8uDL5rrj8gbmwaGEhNHIA1W9+ XGgsZsX/cEjsGUO5qw+2kZhS+8m8ihM50pArhQMYGPA7Rs+YFlYQGmUThhD4u9kGqGNtAhkf5za 9wNa1ohTAQNkCCNIPug== 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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" 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