Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 25452 invoked from network); 21 Jul 2010 22:38:56 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 21 Jul 2010 22:38:56 -0000 Received: (qmail 70076 invoked by uid 500); 21 Jul 2010 22:38:54 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 70030 invoked by uid 500); 21 Jul 2010 22:38:53 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 70022 invoked by uid 99); 21 Jul 2010 22:38:53 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 21 Jul 2010 22:38:53 +0000 X-ASF-Spam-Status: No, hits=4.4 required=10.0 tests=FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_PASS,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of amitabhs2005@gmail.com designates 209.85.216.172 as permitted sender) Received: from [209.85.216.172] (HELO mail-qy0-f172.google.com) (209.85.216.172) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 21 Jul 2010 22:38:46 +0000 Received: by qyk1 with SMTP id 1so3344938qyk.10 for ; Wed, 21 Jul 2010 15:37:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:date:message-id :subject:from:to:content-type; bh=IhD9IKdf4zgTiW8lvmrIUCGn/kUziDy6LpqJIw+qOQc=; b=j2WJh3UqH52CQQ+QHJfjlxd3VpXAKMWKDnIFi5h1mkMq4gOaNCc1x+wG70TlLsbLSz 1EtRLqExMrWjd58I+6gLSA9KdrjRFhU+z6gdH6IEU/w/+l1XhsV66FSo0LdNyb/H0qiY IuMMs0XnQBXA9AbTwrC0oL3XnNinocdzczCy8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=gxXo0K9Ue0sQ0EWLnH56S7HKUXYGPxFv+hSdIP/nVmU56Xi1gm4B/zvRTDh1LoQwbk VwsI7B2bBcTri/+h5HTF5vEkurCM78qZFijqhqWo8HkkSmE1xJYgn8p+iwRfAUzXm+uS F1iL3J1QCWB8mQTpbAZ1RTF/DeIaCCgGPNQA0= MIME-Version: 1.0 Received: by 10.224.88.70 with SMTP id z6mr677113qal.23.1279751845248; Wed, 21 Jul 2010 15:37:25 -0700 (PDT) Received: by 10.229.240.7 with HTTP; Wed, 21 Jul 2010 15:37:25 -0700 (PDT) Date: Wed, 21 Jul 2010 15:37:25 -0700 Message-ID: Subject: Cassandra committing massive virtual memory From: Amit Sinha To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=00c09f97243a230530048bed7277 X-Virus-Checked: Checked by ClamAV on apache.org --00c09f97243a230530048bed7277 Content-Type: text/plain; charset=ISO-8859-1 We are seeing cassandra using very high virtual memory. One server in the cluster shows 90GB and the other shows about 70GB of committed virtual memory. The real memory used is less than 1GB. The Xmx is 4GB. The physical memory on the machine is 32GB and the swap space on the machine is around 20GB. I understand that the virtual memory is not really used by the process and is just reserved. My question is why does cassandra need to reserve such huge memory. What is the logic that is used internally. How is it related to usage pattern or data storage pattern. Should we be concerned? thanks Amit --00c09f97243a230530048bed7277 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable We are seeing cassandra using very high virtual memory. One server in the c= luster shows 90GB and the other shows about 70GB of committed virtual memor= y.
The real memory used is less than 1GB. The Xmx is 4GB. The physical m= emory on the machine is 32GB and the swap space on the machine is around 20= GB.

I understand that the virtual memory is not really used by the process = and is just reserved. My question is why does cassandra need to reserve suc= h huge memory. What is the logic that is used internally. How is it related= to usage pattern or data storage pattern. Should we be concerned?

thanks
Amit



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