Re: drop_caches ...

[Zdenek Kabelac <zkabelac@redhat.com>]

Markus napsal(a):
>>>>>>> The memory mapped pages won't be dropped in this way.
>>>>>>> "cat /proc/meminfo" will show you the number of mapped pages.
>>>>>> # sync ; echo 3 > /proc/sys/vm/drop_caches ; free -m ; 
>>>> cat /proc/meminfo
>>>>>>              total       used       free     shared    buffers     
>>>>>> cached
>>>>>> Mem:          3950       3262        688          0          0        
>>>>>> 359
>>>>>> -/+ buffers/cache:       2902       1047
>>>>>> Swap:         5890       1509       4381
>>>>>> MemTotal:        4045500 kB
>>>>>> MemFree:          705180 kB
>>>>>> Buffers:             508 kB
>>>>>> Cached:           367748 kB
>>>>>> SwapCached:       880744 kB
>>>>>> Active:          1555032 kB
>>>>>> Inactive:        1634868 kB
>>>>>> Active(anon):    1527100 kB
>>>>>> Inactive(anon):  1607328 kB
>>>>>> Active(file):      27932 kB
>>>>>> Inactive(file):    27540 kB
>>>>>> Unevictable:         816 kB
>>>>>> Mlocked:               0 kB
>>>>>> SwapTotal:       6032344 kB
>>>>>> SwapFree:        4486496 kB
>>>>>> Dirty:                 0 kB
>>>>>> Writeback:             0 kB
>>>>>> AnonPages:       2378112 kB
>>>>>> Mapped:            52196 kB
>>>>>> Slab:              65640 kB
>>>>>> SReclaimable:      46192 kB
>>>>>> SUnreclaim:        19448 kB
>>>>>> PageTables:        28200 kB
>>>>>> NFS_Unstable:          0 kB
>>>>>> Bounce:                0 kB
>>>>>> WritebackTmp:          0 kB
>>>>>> CommitLimit:     8055092 kB
>>>>>> Committed_AS:    4915636 kB
>>>>>> VmallocTotal:   34359738367 kB
>>>>>> VmallocUsed:       44580 kB
>>>>>> VmallocChunk:   34359677239 kB
>>>>>> DirectMap4k:     3182528 kB
>>>>>> DirectMap2M:     1011712 kB
>>>>>>
>>>>>> The cached reduced to 359 MB (after the dropping).
>>>>>> I dont know where to read the "number of mapped pages".
>>>>>> "Mapped" is about 51 MB.
>>>>> Does your tmpfs store lots of files?
>>>> Dont think so:
>>>>
>>>> # df -h
>>>> Filesystem            Size  Used Avail Use% Mounted on
>>>> /dev/md6               14G  8.2G  5.6G  60% /
>>>> udev                   10M  304K  9.8M   3% /dev
>>>> cachedir              4.0M  100K  4.0M   3% /lib64/splash/cache
>>>> /dev/md4               19G   15G  3.1G  83% /home
>>>> /dev/md3              8.3G  4.5G  3.9G  55% /usr/portage
>>>> shm                   2.0G     0  2.0G   0% /dev/shm
>>>> /dev/md1               99M   19M   76M  20% /boot
>>>>
>>>> # mount
>>>> /dev/md6 on / type ext3 (rw,noatime,nodiratime,barrier=0)
>>>> /proc on /proc type proc (rw,noexec,nosuid,noatime,nodiratime)
>>>> sysfs on /sys type sysfs (rw,nosuid,nodev,noexec)
>>>> udev on /dev type tmpfs (rw,nosuid,size=10240k,mode=755)
>>>> devpts on /dev/pts type devpts (rw,nosuid,noexec,gid=5,mode=620)
>>>> cachedir on /lib64/splash/cache type tmpfs (rw,size=4096k,mode=644)
>>>> /dev/md4 on /home type ext3 (rw,noatime,nodiratime,barrier=0)
>>>> /dev/md3 on /usr/portage type ext4 
> (rw,noatime,nodiratime,barrier=0)
>>>> shm on /dev/shm type tmpfs (rw,noexec,nosuid,nodev)
>>>> usbfs on /proc/bus/usb type usbfs 
>>>> (rw,noexec,nosuid,devmode=0664,devgid=85)
>>>> automount(pid6507) on /mnt/.autofs/misc type autofs 
>>>> (rw,fd=4,pgrp=6507,minproto=2,maxproto=4)
>>>> automount(pid6521) on /mnt/.autofs/usb type autofs 
>>>> (rw,fd=4,pgrp=6521,minproto=2,maxproto=4)
>>>> /dev/md1 on /boot type ext2 (rw,noatime,nodiratime)
>>>>
>>>> I dont know what exactly all that memory is used for. It varies 
> from 
>>>> about 300 MB to up to one GB.
>>>> Tell me where to look and I will!
>>> So you don't have lots of mapped pages(Mapped=51M) or tmpfs files.  
> It's
>>> strange to me that there are so many undroppable cached 
> pages(Cached=359M),
>>> and most of them lie out of the LRU queue(Active+Inactive 
> file=53M)...
>>> Anyone have better clues on these 'hidden' pages?
>> Maybe try this:
>>
>> cat /proc/`pidof X`/smaps | grep drm | wc -l
>>
>> you will see some growing numbers.
>>
>> Also check  cat /proc/dri/0/gem_objects
>> there should be some number  # object bytes - which should be close to 
> your 
>> missing cached pages.
>>
>>
>> If you are using Intel GEM driver - there is some unlimited caching 
> issue
>> see: http://bugs.freedesktop.org/show_bug.cgi?id=20404
>>
> # cat /proc/`pidof X`/smaps | grep drm | wc -l
> 0
> # cat /proc/dri/0/gem_objects
> cat: /proc/dri/0/gem_objects: No such file or directory
> 
> I use Xorg 1.3 with an nvidia gpu. Dont know if I use a "Intel GEM 
> driver".
> 


Are you using binary  driver from NVidia ??
Maybe you should ask authors of this binary blob ?

Could you try to use for a while Vesa driver to see, if you are able to get 
same strange results ?

Zdenek