Yes it can, but you probably don't want to do that. You definitely don't want to do it in an automated way when the machine is experiencing memory pressure.
There are very good reasons that Linux (and most other modern operating systems) makes aggressive use of page caches and buffers. For the vast majority of applications dropping these caches is going to reduce performance considerably (disk is really really slow) and most applications for which this isn't true are probably using O_DIRECT anyway.
The arguments in favor of page caching are: (a) disks have very high latency (b) disks have relatively low bandwidth (c) for hot data RAM is cheaper disk IO both in dollars and in watts [1] and (d) it's basically free because the memory would have been unused anyway.
The arguments against page caching are: (a) occasionally the kernel will make poor choices and do something sub-optimal and (b) high numbers in 'free' make me feel better.
Too many inexperienced operators (or those experienced on other OSs) confuse disadvantage (a) for disadvantage (b) and decide to drop caches using a cron job.
[1] Old but good: ftp://ftp.research.microsoft.com/pub/tr/tr-97-33.pdf
There are very good reasons that Linux (and most other modern operating systems) makes aggressive use of page caches and buffers. For the vast majority of applications dropping these caches is going to reduce performance considerably (disk is really really slow) and most applications for which this isn't true are probably using O_DIRECT anyway.
The arguments in favor of page caching are: (a) disks have very high latency (b) disks have relatively low bandwidth (c) for hot data RAM is cheaper disk IO both in dollars and in watts [1] and (d) it's basically free because the memory would have been unused anyway.
The arguments against page caching are: (a) occasionally the kernel will make poor choices and do something sub-optimal and (b) high numbers in 'free' make me feel better.
Too many inexperienced operators (or those experienced on other OSs) confuse disadvantage (a) for disadvantage (b) and decide to drop caches using a cron job.
[1] Old but good: ftp://ftp.research.microsoft.com/pub/tr/tr-97-33.pdf