Accelerating swapless machines
in [UK Linux]
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From: alexd on 24 Feb 2010 14:41 On Wed, 24 Feb 2010 19:12:30 +0000, Theo Markettos wrote: > I also keep all my working files on a USB stick, so the SSD only holds > the OS. As an experiment, how about making the SSD as read-only as possible, and mount ~/ on the USB? -- <http://ale.cx/> (AIM:troffasky) (UnSoEsNpEaTm(a)ale.cx) 19:40:32 up 9 days, 31 min, 5 users, load average: 0.00, 0.03, 0.16 DIMENSION-CONTROLLING FORT DOH HAS NOW BEEN DEMOLISHED, AND TIME STARTED FLOWING REVERSELY
From: Jim A on 24 Feb 2010 15:01 Theo Markettos wrote: > I have a Dell Mini 9 netbook running Ubuntu, with 1GB RAM. Most of the time > when I have more than one application running it is tediously slow, to the > point that I sometimes have to wait seconds to switch windows. For example, > at the moment I have: If you add more RAM you can set some of it up as a ramdisk so temporary files and such can be written really quickly. There are some notes on this at http://wiki.eeeuser.com/ubuntu:eeexubuntu:customization?s[]=ramdisk#installation Also, make sure your filesystems are set up not to record the accesstime every time a file is read - for example /etc/fstab on my Mandriva system has: # Entry for /dev/sdb1 : UUID=18a86282-38ef-4ab7-ae17-84efc090b6c1 / ext3 noatime 1 1 # Entry for /dev/sda1 : UUID=0b713340-2372-4dfa-8470-faa3259fe636 /home ext3 noatime 1 2 hth, Jim (on an old Asus Eee upgraded to 2Gb RAM with Mandriva 2009 installed both on the internal 4G flash and an 8G sdhc card). -- www.slowbicyclemovement.org - enjoy the ride
From: Theo Markettos on 24 Feb 2010 16:58 Jim A <ja(a)averyjim.myzen.co.uk> wrote: > If you add more RAM you can set some of it up as a ramdisk so temporary > files and such can be written really quickly. There are some notes on > this at > http://wiki.eeeuser.com/ubuntu:eeexubuntu:customization?s[]=ramdisk#installation Does /tmp actually get thrashed that much on a normal system? (Rather than, say, transferring files between programs which happens relatively rarely) > Also, make sure your filesystems are set up not to record the accesstime > every time a file is read - for example /etc/fstab on my Mandriva > system has: My SSD partition is mounted 'relatime', which is like 'noatime' but doesn't break some apps. Is there a noticeable difference between the two? Theo
From: Jim A on 24 Feb 2010 17:42 Theo Markettos wrote: > Jim A <ja(a)averyjim.myzen.co.uk> wrote: >> If you add more RAM you can set some of it up as a ramdisk so temporary >> files and such can be written really quickly. There are some notes on >> this at >> http://wiki.eeeuser.com/ubuntu:eeexubuntu:customization?s[]=ramdisk#installation > > Does /tmp actually get thrashed that much on a normal system? That depends on what you're running. If some other folder is being thrashed, consider mounting that as a ramdisk instead (so long as you don't mind the contents being trashed on reboot). I've seen recommendations to put the Firefox cache on a ramdisk - which I guess is good advice if you always clear the cache on exit anyway, but if you don't it might actually slow the browser down. > My SSD partition is mounted 'relatime', which is like 'noatime' but doesn't > break some apps. Is there a noticeable difference between the two? I confess I hadn't come across relatime before - it seems it will result in more disk writes than noatime (a quick google will throw up plenty of discussion on the subject). There are (at least) two issues with flash drives. One is that write speeds can be really slow. The other issue is whether excessive writes will eventually wear out the ssd. Having said all this, I'm not currently using ramdisks on this 600mhz Eee, and find Firefox, Thunderbird etc, run acceptably fast except when viewing sites with lots of flash adverts. ymmv -- www.slowbicyclemovement.org - enjoy the ride
From: Gordon Henderson on 24 Feb 2010 22:39
In article <EAy*h6v4s(a)news.chiark.greenend.org.uk>, Theo Markettos <theom+news(a)chiark.greenend.org.uk> wrote: >Paul Rudin <paul.nospam(a)rudin.co.uk> wrote: >> My daughter has a dell mini 10v with Ubuntu and it's fine for normal >> desktop use. The difference is it has a proper hard disc, so I guess >> that adds weight to the idea that the SSD is the problem. > >So is it RAM or SSD I should be thinking of upgrading? On the other laptop, >Linux doesn't thrash disc too much, so I don't think it's waiting for files >to come in. And on the netbook there's no swap, so that won't slow things >down. So is it mmap() that's the problem, and will more RAM help? More RAM will only help if you can move stuff into it as a ramdisk. It's writes to it that will generally cause "clunkyness" - and there is a multitude of things doing the writes that happen behind the scenes... Start with syslog - if it's running (or a variant), then check the config file - any line that ends in a filename - e.g. auth,authpriv.* /var/log/auth.log will cause an fsync on that file for every line written - that'll kill disk performance - the solution is to prefix the filename with a dash, so: auth,authpriv.* -/var/log/auth.log It can be argued that "it's a laptop, no need for syslog or it's variants"... So it might be worthwhile seeing what's actually running and kill it off... >I'm not doing anything particularly file-intensive most of the time (and >I've zapped most of the stuff like updatedb that thrashes disc just for the >hell of it) so I can't see why SSD would cause a direct improvement. You may not be doing disk stuff, but applications will be - web browser will be maintaining a cache and it may well be fsyncing it's index file - same for cookies and browsing history - firefox tries really hard now to try to maintain as much state as possible between crashes... And ext3 is going to be writing to disk every 5 seconds too - there are ways to tune that though - the easiest is to move to ext2, but for a laptop which runs out of juice every now & then, ext3 is handy... >I also keep all my working files on a USB stick, so the SSD only holds the >OS. And temporary files, and working files used by applications... Gordon |