Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 15 Mar 2001 10:54:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 15 Mar 2001 10:54:30 -0500 Received: from clev-max1-cs-8.dial.bright.net ([209.143.46.10]:53889 "EHLO skylab.winds.org") by vger.kernel.org with ESMTP id ; Thu, 15 Mar 2001 10:54:16 -0500 Date: Thu, 15 Mar 2001 10:53:02 -0500 (EST) From: Byron Stanoszek To: Subject: Need help with allocating a 2M buffer size Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I have a real picky tape drive (DLT series) that likes to be fed large chunks of data at once, otherwise after every 2-4KB of data it halts and rewinds itself because its cache for writing to the tape is empty. My best solution to this problem was to use 'tar -b 4096', which sends 4096 x 512-byte blocks at once for a total of a 2MB buffer size. This worked fine for several weeks, until 2 days ago I got this message (and the backup fails): st: failed to enlarge buffer to 2097152 bytes. Free memory shows: total used free shared buffers cached Mem: 517036 514468 2568 751908 47804 189488 -/+ buffers/cache: 277176 239860 Swap: 136544 452 136092 Unfortunately, all of the "free" memory right now is eaten up using cache. Is there a way I can just tell the kernel to allocate memory from the cache for the buffer? I'm sure there's gotta be a 2MB-sized chunk in that 189MB cache -somewhere-. Why doesn't the kernel's get_free_pages() function support moving data around in memory to get larger chunks for what it needs? I see this same problem happening in SVGATextMode where allocating space for a NxM character screen (where NxM >= 16384) fails because there is no contiguous memory space. I think at least it should be able to use some cache. Suggestions? -Byron -- Byron Stanoszek Ph: (330) 644-3059 Systems Programmer Fax: (330) 644-8110 Commercial Timesharing Inc. Email: byron@comtime.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/