Hello Don,
I filed a new merge request for this suggestion. It is now open at the
following URI:
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/673
Perfect. Thanks! I see Justin already accepted it!
Cheers,
Don
Kind regards,
On 29/09/2020 16:34, Don Zickus wrote:
> On Fri, Sep 18, 2020 at 10:49:09AM +0200, Bohdan Khomutskyi wrote:
> > Hello,
> >
> > While working on the change proposal
> >
https://fedoraproject.org/wiki/Changes/OptimizeSquashFS
> >
> > I discovered that several kernel configuration options are set sub-optimally
> > in Fedora. In RHEL 8, the optimal configuration is used.
> > If we set those options to match RHEL 8, a performance improvement could be
> > achieved while reading the SquashFS filesystem.
> >
> > Below you can see an excerpt from the configuration help:
> Would you be willing to submit a merge request with these changes for
> Fedora? Then we can have a discussion and review.
>
> Cheers,
> Don
>
> > Set in RHEL 8:
> >
> > SQUASHFS_FILE_DIRECT
> > ÃÂ ÃÂ ÃÂ ÃÂ Directly decompress file data into the page cache.
> > ÃÂ ÃÂ ÃÂ ÃÂ Doing so can significantly improve performance because
> > ÃÂ ÃÂ ÃÂ ÃÂ it eliminates a memcpy and it also removes the lock
contention
> > ÃÂ ÃÂ ÃÂ ÃÂ on the single buffer.
> >
> > SQUASHFS_DECOMP_MULTI_PERCPU
> > ÃÂ ÃÂ ÃÂ ÃÂ By default Squashfs uses a single decompressor but it gives
> > ÃÂ ÃÂ ÃÂ ÃÂ poor performance on parallel I/O workloads when using
multiple CPU
> > ÃÂ ÃÂ ÃÂ ÃÂ machines due to waiting on decompressor availability.
> >
> > ÃÂ ÃÂ ÃÂ ÃÂ This decompressor implementation uses a maximum of one
> > ÃÂ ÃÂ ÃÂ ÃÂ decompressor per core.ÃÂ It uses percpu variables to
ensure
> > ÃÂ ÃÂ ÃÂ ÃÂ decompression is load-balanced across the cores.
> >
> > Set in Fedora:
> > SQUASHFS_DECOMP_SINGLE
> > ÃÂ ÃÂ ÃÂ ÃÂ Traditionally Squashfs has used single-threaded
decompression.
> > ÃÂ ÃÂ ÃÂ ÃÂ Only one block (data or metadata) can be decompressed at any
> > ÃÂ ÃÂ ÃÂ ÃÂ one time.ÃÂ This limits CPU and memory usage to a minimum.
> >
> > SQUASHFS_FILE_CACHE
> > ÃÂ ÃÂ ÃÂ ÃÂ Decompress file data into an intermediate buffer and then
> > ÃÂ ÃÂ ÃÂ ÃÂ memcopy it into the page cache.
> >
> > The SquashFS filesystem is used on installation medium. So making the change
> > I propose should improve the user experience during installation. It should
> > also improve the user experience while booting from Fedora Live image.
> >
> > Kind regards,
> >
> > --
> > Bohdan Khomutskyi
> > Software engineer
> > Red Hat
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--
Bohdan Khomutskyi
Software engineer
Red Hat