Re: dd: avoid swap and benchmark of the nocache option

[Francois]

On 12 January 2016 at 12:19, Pádraig Brady <address@hidden> wrote:
> On 11/01/16 23:19, Francois wrote:
>> On 11 January 2016 at 23:55, Pádraig Brady <address@hidden> wrote:

>>> syncing should be a very explicit thing and carefully considered.

> Right. But didn't doing that take 300% more "sys" time,
> while not providing much benefits over oflag=nocache,sync ?

I thinks that's the deal: if you want to copy files in this fashion use
nocache,sync. In our case, the nocache option alone is useless, and you
really do want to consider syncing.

Looking again at the benchmarks, we see that the nocache,sync option
does seem to consume more memory (like ten times more) than the updated
nocache option without sync. Might be worth to check how fadvise is
implemented, and what's taking CPU time. (I make a post-it)

Cheers!