From: Jeff D. <jd...@ka...> - 2002-01-01 02:18:51
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sf...@ih... said: > If I hit a page several times with this on the host, the disk just > twitches a few times as it writes its logs. When I do the same to it > running under UML, there is considerable disk activity. Is this > typical? You might be seeing physical memory activity, which is mmapped out of a file on disk. Try mounting tmpfs as your /tmp and see if disk activity subsides. At some point, I'm going to have UML mmap /dev/zero on 2.4 hosts instead of mmapping temporary files on disk. This should be equivalent to tmpfs. Jeff |
From: Jeff D. <jd...@ka...> - 2002-01-01 04:22:36
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sf...@ih... said: > Sorry, you'll have to give me the kiddy treatment. You mean the UML's > memory went to swap on the host? Adam gave a good answer to this except for this bit: ad...@do... said: > So, any access to the UML memory means disk access will happen on the > host. That's actually up to the host VM system and filesystem. They will generally try to keep stuff in memory and off of disk for as long as possible (except for the update daemon flushing all file data out periodically). I think the VM system should treat ext2 data and tmpfs data the same. It's all in the page cache and I don't think it cares who owns it. However, ext2 (and other on-disk filesystems) have their own reasons for wanting to put stuff on disk when the VM system wouldn't have. I would guess that this difference accounts for the performance differences between ext2 and tmpfs. Jeff |
From: Jeff D. <jd...@ka...> - 2002-01-05 03:50:44
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xi...@bo... said: > Is UML hardcoded to use /tmp for the mmapped memory, or can another > dir be specified at runtime? It respects the TMP, TEMP, and TMPDIR environment variables. Jeff |
From: Christian L. <xi...@bo...> - 2002-01-05 12:46:56
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Jeff Dike <jd...@ka...> writes: > xi...@bo... said: > > Is UML hardcoded to use /tmp for the mmapped memory, or can another > > dir be specified at runtime? > > It respects the TMP, TEMP, and TMPDIR environment variables. Thank you, that did the trick. ('killall -STOP kupdated' gave me nice performance but seemed just a little bit too dangerous. ;-) -- Med venlig hilsen Christian Laursen |
From: Steve F. <sf...@ih...> - 2002-01-01 02:30:31
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> You might be seeing physical memory activity, which is mmapped out of a > file on disk. Sorry, you'll have to give me the kiddy treatment. You mean the UML's memory went to swap on the host? > Try mounting tmpfs as your /tmp and see if disk activity subsides. Sorry, where do I find the instructions to do this? I'm glad to help, but I've never heard of tmpfs before. Steve |
From: Rob F. <rf...@ke...> - 2002-01-01 03:26:13
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try something like this in your /etc/fstab: none /tmp shm defaults 1 1 On Mon, 31 Dec 2001 18:30:23 -0800 Steve Freitas <sf...@ih...> wrote: > > You might be seeing physical memory activity, which is mmapped out of a > > file on disk. > > Sorry, you'll have to give me the kiddy treatment. You mean the UML's memory > went to swap on the host? > > > Try mounting tmpfs as your /tmp and see if disk activity subsides. > > Sorry, where do I find the instructions to do this? I'm glad to help, but > I've never heard of tmpfs before. > > Steve > > > _______________________________________________ > User-mode-linux-user mailing list > Use...@li... > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user -- Rob Fowler rf...@ke... |
From: Rob F. <rf...@ke...> - 2002-01-01 03:31:21
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tmpfs is a fantastic addition. (It speeds up the kernel compile by 2 on one of my slower machines!) =46rom the linux kernel documentation: Tmpfs is a file system which keeps all files in virtual memory. In contrast to RAM disks, which get allocated a fixed amount of physical RAM, tmpfs grows and shrinks to accommodate the files it contains and is able to swap unneeded pages out to swap space. Everything is "virtual" in the sense that no files will be created on your hard drive; if you reboot, everything in tmpfs will be lost. You should mount the file system somewhere to be able to use POSIX shared memory. Adding the following line to /etc/fstab should take care of things: tmpfs /dev/shm tmpfs defaults 0 0 Remember to create the directory that you intend to mount tmpfs on if necessary (/dev/shm is automagically created if you use devfs). You can set limits for the number of blocks and inodes used by the file system with the mount options "size", "nr_blocks" and "nr_inodes". These parameters accept a suffix k, m or g for kilo, mega and giga and can be changed on remount. The initial permissions of the root directory can be set with the mount option "mode". On Mon, 31 Dec 2001 18:30:23 -0800 Steve Freitas <sf...@ih...> wrote: > > You might be seeing physical memory activity, which is mmapped out of a > > file on disk. >=20 > Sorry, you'll have to give me the kiddy treatment. You mean the UML's mem= ory > went to swap on the host? >=20 > > Try mounting tmpfs as your /tmp and see if disk activity subsides. >=20 > Sorry, where do I find the instructions to do this? I'm glad to help, but > I've never heard of tmpfs before. >=20 > Steve >=20 >=20 > _______________________________________________ > User-mode-linux-user mailing list > Use...@li... > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user --=20 Rob Fowler rf...@ke... |
From: Adam H. <ad...@do...> - 2002-01-01 03:39:02
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On Mon, 31 Dec 2001, Steve Freitas wrote: > > You might be seeing physical memory activity, which is mmapped out of a > > file on disk. > > Sorry, you'll have to give me the kiddy treatment. You mean the UML's memory > went to swap on the host? A file of size X is created on the host's disk. This file is then memory mapped by uml, and all of its children. The UML nodes use this file to hold their memory. So, any access to the UML memory means disk access will happen on the host. |
From: Christian L. <xi...@bo...> - 2002-01-05 02:53:17
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Jeff Dike <jd...@ka...> writes: > sf...@ih... said: > > If I hit a page several times with this on the host, the disk just > > twitches a few times as it writes its logs. When I do the same to it > > running under UML, there is considerable disk activity. Is this > > typical? > > You might be seeing physical memory activity, which is mmapped out of a > file on disk. Try mounting tmpfs as your /tmp and see if disk activity > subsides. Is UML hardcoded to use /tmp for the mmapped memory, or can another dir be specified at runtime? -- Med venlig hilsen Christian Laursen |