[ale] Disk performance

[Alex Carver]

On 8/24/2013 18:03, Ed Cashin wrote:
> On Sat, Aug 24, 2013 at 8:38 PM, Alex Carver <agcarver+ale at acarver.net>wrote:
> ...
>
>> Well, looks like mostly still working although it has a memory leak
>> somewhere.  The free memory (according to top) is slowly dropping.  It went
>> from 380MB to 365MB in about two hours so 15MB went somewhere during that
>> time.  Probably one of the cron jobs or apache, just don't know which yet.
>>
>
> If you haven't already, you might check whether that memory is simply being
> used to cache stuff.  Linux aggressively caches blocks from disk in pages
> of memory, which is usually a convenience.

The free memory went further down by morning but /proc/meminfo seems to 
indicate that most of the used memory is cache.  The two largest 
processes (apache and mysql) haven't changed much in their resident, 
data, virtual or swap usage since last night.  So disk cache it must be. 
  Any way to tune the amount of cache it retains or how often it flushes 
unused disk pages?

MemTotal:         515356 kB
MemFree:          170708 kB
Buffers:           23080 kB
Cached:           253568 kB
SwapCached:           44 kB
Active:           268980 kB
Inactive:          54828 kB
Active(anon):       8372 kB
Inactive(anon):    40504 kB
Active(file):     260608 kB
Inactive(file):    14324 kB

AnonPages:         47140 kB
Mapped:            21844 kB
Shmem:              1716 kB
Slab:              15852 kB
SReclaimable:      12176 kB
SUnreclaim:         3676 kB
KernelStack:         776 kB
PageTables:         1216 kB