Re: Downsides to madvise/fadvise(willneed) for application startup

[Wu Fengguang]

Minchan,

> A few month ago, I saw your patch about enhancing readahead.
> At that time, many guys tested several size of USB and SSD which are
> consist of nand device.
> The result is good if we does readahead untile some crossover point.
> So I think we need readahead about file I/O in non-rotation device, too.
> 
> But startup latency is important than file I/O performance in some machine.
> With analysis at that time, code readahead of application affected slow startup.
> In addition, during bootup, cache hit ratio was very small.
> 
> So I hoped we can disable readahead just only code section(ie, roughly
> exec vma's filemap fault). :)
> 
> I don't want you to solve this problem right now.
> Just let you understand embedded system's some problem
> for enhancing readahead in future.  :)

Yeah, I've never heard of such a demand, definitely good to know it!

Thanks,
Fengguang
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