On Fri, Feb 01, 2002 at 12:11:45PM -0800, William Lee Irwin III wrote:
> On Fri, Feb 01, 2002 at 11:24:16AM -0800, Adam McKenna wrote:
> > adam@xpdb:~$ uptime
> > 11:21am up 42 days, 18:53, 3 users, load average: 54.72, 21.21, 17.60
> > adam@xpdb:~$ free
> > total used free shared buffers cached
> > Mem: 5528464 5522744 5720 0 476 5349784
> > -/+ buffers/cache: 172484 5355980
> > Swap: 2939804 1302368 1637436
> > As you can see, there are supposedly 5.3 gigs of memory free (not counting
> > memory used for cache). However, the box is swapping like mad (about 10 megs
> > every 2 seconds according to vmstat) and the load is skyrocketing.
>
> That 5.3GB is without kernel caches. I see 5.7MB...
>
> On Fri, Feb 01, 2002 at 11:24:16AM -0800, Adam McKenna wrote:
> > Now top, on the other hand, has a very different idea about the amount of
> > free memory:
> > CPU states: 0.0% user, 0.1% system, 0.1% nice, 0.0% idle
> > Mem: 5528464K av, 5523484K used, 4980K free, 0K shrd, 340K buff
> > Swap: 2939804K av, 1082008K used, 1857796K free 5351892K
> > cached
>
> They actually agree. The line you're reading with 5.3GB in it subtracts
> kernel caches from the memory in use.
>
> The fun bit about swapping like mad is because kernel caches are not
> being flushed and shrunk properly in response to growth of the working
> set. In more concrete terms, the kernel is making decisions which prefer
> to keep things like the page cache, the dentry cache, the inode cache,
> and the buffer cache in memory over the working sets of your programs.
> There is some tradeoff: it is probably also not desirable to allow the
> working set to erode kernel caches to the absolute minimum (or at least
> not very easily), but obviously what tradeoffs are happening here are
> suboptimal for your workload (and generally insufficiently adaptive). It
> appears that when the kernel caches are done with you you've got 172MB
> out of 5.5GB of physical memory left for your programs' anonymous memory.
>
> What kernel/VM are you using?
2.4.6-xfs but we've also seen this with 2.4.14-xfs (xfs 1.0.2 release)
> Could you follow up with /proc/slabinfo and /proc/meminfo?
We've already rebooted the box, next time we are experiencing the problem
I'll send this info.
Meanwhile, is there any way to tune the kernel cache?
--Adam
-- Adam McKenna <adam@flounder.net> | GPG: 17A4 11F7 5E7E C2E7 08AA http://flounder.net/publickey.html | 38B0 05D0 8BF7 2C6D 110A - 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/
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