From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) (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 637202C08BB for ; Fri, 18 Sep 2026 00:22:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789690972; cv=none; b=ZhYWDnMHTYo37AiTKNptsRlQB8arhkuIqTF27jYoKz6gWakoULWD5orfpYnQu3b4sLFxLFu8OmxcA59DB3DDG3HGBSg26h/ggcJaS4yGvqewZFqZxKcYveB/PL1MQMtUfMmiKTgKSWnwhR71kpLYjE6VuatrjGesdAesxLPRMDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789690972; c=relaxed/simple; bh=SNaO/tSW8mgE1+CYp8wV7DdFq/mJq3fdOLd/OcWdgZk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=WslLnJAgYMQp02uOL4FnJbWDvjCFt0+SPuEHBkIAWw1srmlgenD5rs/xar1MOFb0f9PAjMHQmEYHgvOwK3UVYn1C6jJGqrj1XU0mS4LO17l+pLYviPwKQZcmCt8PGFGpRj06+p5E4DIfQk8UJsfWKb+r3xe0AxMEsicHRhK14tI= 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=donODBXp; arc=none smtp.client-ip=209.85.218.70 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="donODBXp" Received: by mail-ej1-f70.google.com with SMTP id a640c23a62f3a-c2967165d94so11184966b.3 for ; Thu, 17 Sep 2026 17:22:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789690963; x=1790295763; 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=2457T8NXpe+VYhyIx4NQQZX9J7v7gQmMrsUW0L2lVQ0=; b=donODBXpW0e9Klrg+W2xegN031w6C+79ec3cQLA3rtz8FfLHcEbndNFcLBNRFDjxas ZhJsK2RgQ8NbgkO9r6oFzznsXdr5a1xBbhLTH0OacKRgrWcIC7Krv4X8hb6vYSQYsWi3 2c0K9Xm6i5d24RLOdU7Fr/qztVaOco53aBuw/5wrNmL2IKdlAE6zcgr0wnQw5HWVE2VP Uubz35UAVkVeAk3tMA7Zy2UIwWWxfLacRJaGXlYDzI2wRY+4FDzS2fO+z3Ru47lBh/eM cgnFG8xGzQkbOFGzSK3A7fAD7DH8BdNE1mFk9UCqELIVnuiIW1FfLdUh1OPoX35UOUEu f6YQ== 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=RscSgqg1EMOqnKEFnjKcA+ekHoNre6UPqrSnx8XZkWxUyeb280UIEmg02JxkzQSkzv IL6C9eWJJlsg9yVbcfp1Uimp+66HXBlRBoy+X/Bhf/hpnYVFT8QHrfY16x6UE0z94qkl omLDHxIBpagKQVhwb5y/LI7gMaZHRx1q++Ha54RcWvDy6U8doie+Xv5ws/3KOcHHDzSJ WwDxHOGiqXKLPLYJ21BhIhr53lExNt+ZZLf1hNGauKGICTIpMv2NmAsWeea20zJmL3y7 8AtmHQWCMDOju+fMCpKI30mcHQPahn2fI4MJjy3qXeAmeUJbQ1Cez+jSR37KCe7XL7Au jFUg== X-Gm-Message-State: AFuF++nAtKPSfFIJGPrCbfyHPOgkykIHCdOPmeLszdZQ4xbScjpNXNPi JA4eZITsb8Z8eYP7VboOYnOg5+tLI4McbWduyfpnK4AIhPu05We/uoyTfhUJiMHCVsVUtiqAkN9 uBoNApzJ97stqfbLWpQ== 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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" 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