Messages in this thread | | | Date | Wed, 4 Mar 2009 19:05:58 +0800 | From | Wu Fengguang <> | Subject | Re: drop_caches ... |
| |
On Wed, Mar 04, 2009 at 12:32:02PM +0200, Markus wrote: > Hello Fengguang! > > > Hi Markus, > > > > On Wed, Mar 04, 2009 at 10:57:33AM +0100, Markus wrote: > > > Hello! > > > > > > I have a small problem. Maybe its just a misunderstanding but I cant > > > solve it. > > > > > > I think that writing "3" to drop_caches should drop all buffers and > > > caches which are already written. So its recommended to put a "sync" > > > infront of it. > > > So I did "free -m ; sync ; echo 3 > /proc/sys/vm/drop_caches ; > free -m" > > > And it gave me: > > > total used free shared buffers > > > cached > > > Mem: 3950 3922 28 0 1 > > > 879 > > > -/+ buffers/cache: 3041 909 > > > Swap: 5342 205 5136 > > > total used free shared buffers > > > cached > > > Mem: 3950 3907 43 0 0 > > > 864 > > > -/+ buffers/cache: 3041 908 > > > Swap: 5341 206 5135 > > > > > > So the buffer was 1 and is 0 afterthat. But cached is at 879 MB > before > > > and is still 864 MB (!!!) after that! > > > > > > I am at swappiness=0 and when I remove and readd one swap-partition > > > after another (so there is always swap). It will keep the cached and > > > put the swapped memory on other swaps?! > > > > > > I _think_ thats not the way it should go? > > > > > > It would be really kind if someone could explain that issue and > > > what "cached" is at all! > > > > 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?
Thanks, Fengguang
| |