Re: [PATCH] mm/fadvise: discard partial pages iff endbyte is also eof

[åå(Caspar)]

On 2018/1/4 14:13, åå(Caspar) wrote:
> This patch is trying to help to solve a real issue. Sometimes we need to 
> evict the whole file from page cache because we are sure it will not be 
> used in the near future. We try to use posix_fadvise() to finish our 
> work but we often see a "small tail" at the end of some files could not 
> be evicted, after digging a little bit, we find those file sizes are not 
> page-aligned and the "tail" turns out to be partial pages.
>
> We fail to find a standard from posix_fadvise() manual page to subscribe 
> the function behaviors if the `offset' and `len' params are not 

Oops, I find a 'standard' documented in latest man-pages.git[1], blame 
my centos7, it runs with an old man-pages.rpm :-(

Thanks,
Caspar

[1] 
https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?h=ceb1c326b9f3e863dfd9bf33bc7118bb1fa29bfc

> page-aligned, then we go to kernel tree and see this:
>
>  ÂÂÂÂÂÂÂ /*
>  ÂÂÂÂÂÂÂÂ * First and last FULL page! Partial pages are deliberately
>  ÂÂÂÂÂÂÂÂ * preserved on the expectation that it is better to preserve
>  ÂÂÂÂÂÂÂÂ * needed memory than to discard unneeded memory.
>  ÂÂÂÂÂÂÂÂ */