Re: Question about memory usage in 2.4 vs 2.2

Josh Grebe (squash@primary.net)
Tue, 20 Mar 2001 14:29:01 -0600 (CST)


slabinfo reports:

inode_cache 189974 243512 480 30439 30439 1 : 124 62
dentry_cache 201179 341940 128 11398 11398 1 : 252 126

However, I am hard pressed to find documentation on how to actually read
this data, especially on a SMP box. Could someone give me a brief
runwdown?

Also, if this memory is cached, wouldn't it make sense if it were reported
as part of the total cached memory in /proc/meminfo? And can this
behavior be tuned so that it uses less of the overall memory?

Thanks,

Josh

---
Josh Grebe
Senior Unix Systems Administrator
Primary Network, an MPower Company
http://www.primary.net

On Tue, 20 Mar 2001, Jan Harkes wrote:

> On Tue, Mar 20, 2001 at 11:01:52AM -0600, Josh Grebe wrote: > > Greetings, > > > > I have a server farm made of identical hardware running pop3 and imap mail > > functions. recently, we upgraded all the machines to kernel 2.4.2, but we > > noticed that according to free, our memory utilization went way up. Here > > is the output of free on the 2.4.2 machine: > > total used free shared buffers cached > > Mem: 513192 492772 20420 0 1684 263188 > > -/+ buffers/cache: 227900 285292 > > Swap: 819304 540 818764 > > > > > > On the 2.2..18 machine: > > total used free shared buffers cached > > Mem: 517256 351280 165976 19920 82820 186836 > > -/+ buffers/cache: 81624 435632 > > Swap: 819304 0 819304 > > > > > > Doing the math, the 2.4 machine is using 44% of available memory, while > > the 2.2 is using only about 14%. > > What does /proc/slabinfo report for the number of pages locked down in > the inode and dentry caches? My machine has pretty much every inode in > memory and is using close to 50% of my memory for these (214MB/512MB). > > These caches do not seem to be counted towards 'reclaimable' memory by > the new VM and are only pruned when _all_ other attempts to free up > memory have failed. > > This becomes very noticeable on a not very fast, small memory machine > (i.e. 48MB sparc-IPC), where 2.2 stays relatively snappy, but 2.4 > becomes unusable after an updatedb run. > > Jan >

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