Unfortunately, the only machine I have access to with an HDD as
the system drive is running Ubuntu 20.04 LTS, which doesn’t have a
multi-threaded version of fixfiles. So I can’t test this on an
HDD-only system.
Still, here are the timings on a 4-core Atom machine with a SATA SSD and a large SATA HDD data drive mounted at /srv:
$ sudo bash -c 'sync; for i in $(seq 1 3); do echo $i > /proc/sys/vm/drop_caches; done; time fixfiles -T 1 restore'
[…]
real 6m39.521s
user 5m6.599s
sys 0m42.000s
$ sudo bash -c 'sync; for i in $(seq 1 3); do echo $i > /proc/sys/vm/drop_caches; done; time fixfiles -T 0 restore'[…]
real 3m16.602s
user 5m25.444s
sys 0m50.843s
I took care to drop various kernel caches, especially including dentry and inode caches, to make this more reproducible.
Here are the timings on a very modern 16-core machine with NVMe SSD storage:
$ sudo bash -c 'sync; for i in $(seq 1 3); do echo $i > /proc/sys/vm/drop_caches; done; time fixfiles -T 1 restore'
[…]
real 3m17.277s
user 2m42.447s
sys 0m24.403s
$ sudo bash -c 'sync; for i in $(seq 1 3); do echo $i > /proc/sys/vm/drop_caches; done; time fixfiles -T 0 restore'[…]
real 0m58.154s
user 4m27.209s
sys 0m58.127s
On Mon, Jul 18, 2022 at 6:44 AM Petr Lautrbach <plautrba@xxxxxxxxxx> wrote:Dan Čermák <dan.cermak@xxxxxxxxxxxxxxxxxx> writes:Just out of curiosity, how large is the speedup typically?It depends on the number of threads your machine has. But you could get some data for comparison using `fixfiles -T 1 restore` and `fixfiles -T 0 restore` on a running system. The following times are reported on my workstation:Has anyone run such a test on a system using classic ("spinning rust") HDDs? It is sometimes the case that parallelizing activities that are I/O intensive can result in excessive seek activity that can result in rather elongated elapsed times (much worse than single threaded operation). _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
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