With Fedora being intended as a desktop platform, why are these settings
not the default?
The highest priority for a desktop system is to keep the user experience
flowing smoothly, not to maximize disk i/o rates.
Can this be fixed in time for F34? Do we need a bug report?
On 3/23/21 2:26 PM, Roger Heflin wrote:
> This won't speed up the actual IO but it should reduce the impact on other work.
>
> if you aren't familiar, man sysctl to understand how to apply the
> below settings.
>
> set these 2:
> vm.dirty_background_bytes = 3000000
> vm.dirty_bytes = 5000000
>
>
> They will be 0 to start with and these 2 settings will be was was used
> prior to setting bytes:
> vm.dirty_background_ratio = 0
> vm.dirty_ratio = 0
>
>
> ratio is % of memory. So 16GB * (dirty_ratio -
> dirty_background_ratio) / write_rate (guess say 50MB, could be 2x
> either way) and that is how long once you hit dirty_ratio it takes for
> the IO to unfreeze when you hit dirty_background_ratio. It takes
> 2-3 seconds to clear 1% on of 16GB so bigger numbers are much worse.
>
> I set mine so that really I only have 2MB to clear and that will clear
> before I notice. And overall about all the big write cache does for
> you is to give you the false sense with smaller writes that they are
> done when really they are not.
>
> grep -i dirty /proc/meminfo will show you how much you have
> outstanding, and it will bounce between the 2 settings.
>
> On Tue, Mar 23, 2021 at 9:39 AM Richard Shaw <hobbes1069(a)gmail.com> wrote:
>> I'm getting significant iowait while writing to a 100GB file. I have already
made it nocow by copying it to another directory, marking the director nocow (+C) and
using cat <oldfile> <newfile> to re-create it from scratch.
>>
>> I was under the impression that this should fix the problem.
>>
>> On a tangent, it took about 30 minutes to delete the old file... My system is a
Ryzen 5 3600 w/ 16GB or memory but it is a spinning disk. I use an NVME for the system and
the spinning disk for /home.
>>
>> Currently I'm getting random GUI freezes due to the iowait problem and my HDD
indicator light basically stays on solid for over an hour now.
>>
>> Any tips?
>>
>> Thanks,
>> Richard
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