Re: ostree create-usb performance

Thanks for the reply Dan. I put some results from trying perf and strace on
github here:

Seems like time is mostly spent on compression and --disable-fsync works as
advertised, if I'm reading them correctly.

On Wed, Mar 3, 2021 at 10:12 PM Dan Nicholson <dbn endlessos org> wrote:

On Wed, Mar 3, 2021 at 7:18 PM Phaedrus Leeds via ostree-list
<ostree-list gnome org> wrote:

Unfortunately the performance of the create-usb command is well below what one would expect from a modern 
computer: it takes about 63 minutes to copy 8092 MiB which works out to 2.14 MiB/s, on a computer that 
can easily do 85 MiB/s when copying much of the same data packed into a static delta with "ostree 
static-delta generate". At least two things might be the culprit of the slow performance when using 
create-usb instead of a static delta: (1) there is an inherent performance limitation when copying 
several thousand individual files instead of a static delta composed of a few files because of the extra 
work of filesystem operations at the stop and start of each file, or (2) the reduced performance is due 
to all the `fsync()` calls ostree makes during the copy. That latter theory seems experimentally ruled 
out because the performance is comparable if one uses `ostree create-usb --disable-fsync` followed by a 
`sync` command. The former theory probably is a large part of the problem but perhaps there is some way 
we can do better? Any ideas?

Have you tried profiling it? perf could get a pretty good
understanding of where the time is going. You might also try strace to
confirm that ostree is really not calling fsync.

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