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[192.55.52.93]) by mx.google.com with ESMTPS id q15si29938072pfh.284.2019.07.30.14.15.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Jul 2019 14:15:58 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of sathyanarayanan.kuppuswamy@linux.intel.com designates 192.55.52.93 as permitted sender) client-ip=192.55.52.93; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of sathyanarayanan.kuppuswamy@linux.intel.com designates 192.55.52.93 as permitted sender) smtp.mailfrom=sathyanarayanan.kuppuswamy@linux.intel.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Jul 2019 14:15:57 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,327,1559545200"; d="scan'208";a="196059110" Received: from linux.intel.com ([10.54.29.200]) by fmsmga004.fm.intel.com with ESMTP; 30 Jul 2019 14:15:57 -0700 Received: from [10.54.74.33] (skuppusw-desk.jf.intel.com [10.54.74.33]) by linux.intel.com (Postfix) with ESMTP id DA4F65803A5; Tue, 30 Jul 2019 14:15:56 -0700 (PDT) Reply-To: sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH v1 1/1] mm/vmalloc.c: Fix percpu free VM area search criteria To: Dave Hansen , Uladzislau Rezki Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190729232139.91131-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20190730204643.tsxgc3n4adb63rlc@pc636> From: sathyanarayanan kuppuswamy Organization: Intel Message-ID: <9fdd44c2-a10e-23f0-a71c-bf8f3e6fc384@linux.intel.com> Date: Tue, 30 Jul 2019 14:13:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/30/19 1:54 PM, Dave Hansen wrote: > On 7/30/19 1:46 PM, Uladzislau Rezki wrote: >>> + /* >>> + * If required width exeeds current VA block, move >>> + * base downwards and then recheck. >>> + */ >>> + if (base + end > va->va_end) { >>> + base = pvm_determine_end_from_reverse(&va, align) - end; >>> + term_area = area; >>> + continue; >>> + } >>> + >>> /* >>> * If this VA does not fit, move base downwards and recheck. >>> */ >>> - if (base + start < va->va_start || base + end > va->va_end) { >>> + if (base + start < va->va_start) { >>> va = node_to_va(rb_prev(&va->rb_node)); >>> base = pvm_determine_end_from_reverse(&va, align) - end; >>> term_area = area; >>> -- >>> 2.21.0 >>> >> I guess it is NUMA related issue, i mean when we have several >> areas/sizes/offsets. Is that correct? > I don't think NUMA has anything to do with it. The vmalloc() area > itself doesn't have any NUMA properties I can think of. We don't, for > instance, partition it into per-node areas that I know of. > > I did encounter this issue on a system with ~100 logical CPUs, which is > a moderate amount these days. I agree with Dave. I don't think this issue is related to NUMA. The problem here is about the logic we use to find appropriate vm_area that satisfies the offset and size requirements of pcpu memory allocator. In my test case, I can reproduce this issue if we make request with offset (ffff000000) and size (600000). > -- Sathyanarayanan Kuppuswamy Linux kernel developer