Is maximum swap usage tunable?

[Warner Losh]

On Fri, Mar 2, 2018 at 5:43 PM, bob prohaska <fbsd at www.zefox.net> wrote:

> On Fri, Mar 02, 2018 at 10:15:57AM -0700, Ian Lepore wrote:
>
> > You forgot a cause: (5) swap is on an sdcard where taking 30-90 seconds
> > to complete an IO is "normal".
> >
> FWIW, the Sandisk Extreme USB flash drive is claimed to be considerably
> faster than that, ~2MB/sec random write, at least per
> http://usb.userbenchmark.com/SanDisk-Extreme-USB-30-16GB/Rating/1301
> One hopes(!) that the microSD cards of the same name are simlar.


Hope in one hand and spit in the other and see which one gets wet first :)

The problem isn't the steady-state happy-state streaming pictures/video to
the card. The problem is that sometimes the "long tail" times for the I/O
for pathological cases can be seconds, or tends of seconds. It doesn't take
too many of those high-latency I/Os to really screw up the system....

SD card FTLs are 'go fast for streaming video / pictures, suck slow for
everything else'. Consumer grade SSDs, though they also have kinda crappy
FTLs, aren't anywhere near that bad.

Warner