From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3CAD3632.E14560B@zip.com.au> Date: Thu, 04 Apr 2002 21:29:22 -0800 From: Andrew Morton MIME-Version: 1.0 Subject: Re: 2.2.20 suspends everything then recovers during heavy I/O References: <4.2.0.58.20020404140237.00b6c390@london.rubylane.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Jim Wilcoxson Cc: linux-mm@kvack.org List-ID: Jim Wilcoxson wrote: > > I'm setting up a new system with 2.2.20, Ingo's raid patches, plus > Hedrick's IDE patches. > > When doing heavy I/O, like copying partitions between drives using tar in a > pipeline, I've noticed that things will just stop for long periods of time, > presumably while buffers are written out to the destination disk. The > destination drive light is on and the system is not exactly hung, because I > can switch consoles and stuff, but a running vmstat totally suspends for > 10-15 seconds. > > Any tips or patches that will avoid this? If our server hangs for 15 > seconds, we're going to have tons of web requests piled up for it when it > decides to wakeup... > Which filesystem are you using? First thing to do is to ensure that your disks are achieving the expected bandwidth. Measure them with `hdparm -t'. If the throughput is poor, and they're IDE, check the chipset tuning options in your kernel config and/or tune the disks with hdparm. If all that fails, you can probably smooth things out by tuning the writeback parameters in /proc/sys/vm/bdflush (if that's there in 2.2. It's certainly somewhere :)) Set the `interval' value smaller than the default five seconds, set `nfract' higher. Set `age_buffer' lower.. And finally: don't go copying entire partitions around on a live web server :) - -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/