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* Fabiano Fidêncio (fidencio at redhat.com) wrote:
> Snir,
> 
> Firstly, let me reply to one specific bit of your email and also add a question.
> 
> [...]
> 
> > IIUC it's currently enabled by default (qemu), can it be disabled? if
> > not, is it planned to be configurable?
> 
> The current govmm codes only sets the "cache-size" when it's different
> from zero:
> https://github.com/intel/govmm/blob/master/qemu/qemu.go#L1256-L1258
> 
> So, setting virtio_fs_cache_size here
> https://github.com/kata-containers/kata-containers/blob/2.0-dev/src/runtime/cli/config/configuration-qemu-virtiofs.toml.in#L113-L114
> disables DAX.
> 
> A question I'd like to add to Snir's question is ...
> Wouldn't it be safer to have `virtio_fs_cache_size = 0` as a default
> value when using virtio-fs, at least till DAX gets solid?

I think that should work; the current qemu vhost-user-fs.c code has:

    DEFINE_PROP_SIZE("cache-size", VHostUserFS, conf.cache_size, 0),

so ommitting the property should give us 0 and cache disabled and
ommitting the property also means you work with upstream qemu's.

I do remember in older dev branches we had the default none-0
but finally found the error of our ways.

Dave


> [...]
> 
> Best Regards,
> -- 
> Fabiano Fidêncio
> 
> 
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-- 
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK