Re: Re: [OE-core] [PATCH] opkg: enable zstd support

[Alex Stewart <alex.stewart@ni.com>]

On 9/13/22 15:20, Alex Feinman wrote:
> I do have some numbers. When I was selling this change internally, I 
> did a comparison on our internal build.
>            Combined write IPK times (Σ t do_package_write_ipk)
> xz         162m 35s
> gz         52m 13s
> zstd       33m 49s
> Compression rate for zstd was closer to xz than to gz but not as good 
> as xz. For systems that have to cache packages on the device with 
> limited storage xz might be a better option, but for the bulk of 
> projects zstd is the best choice
> Additionally, zstd offers much faster decompression than xz so the 
> rootfs build step that includes unpacking all of the ipks, takes 3m 
> 58s with xz and 2m 44s with zstd.
> One other thing of note - if your build includes debug packages, some 
> may be quite large. E.g. one of our components produces a 2.2 GB debug 
> package (uncompressed). On large files xz requires a disproportionally 
> large amount of time resulting in 15 minutes needed to simply write 
> ipk for the abovementioned packages, whereas zstd took about 45 sec. 
> For frequent tasks like bitbaking a single package this translates in 
> a lot of saved time.

Those are certainly compelling performance improvements. Assuming that 
the final data-segment size is within 5%-ish of xz, then I would agree 
with the rest of the thread that it should probably be the contemporary 
default.

And if we make it the default compressor for OE IPKs, then obviously my 
criticism in the original PR is satisfied.

> Bottom line - I think making xz a default package compressor was not 
> entirely thought through. gzip or zstd is what the default should be.

ZStandard support was only added to opkg last September [1]. Before 
that, xz was the new hotness that replaced gzip. :)

[1] 
https://git.yoctoproject.org/opkg/commit/?id=5dead419e94bce2e6b743ad786c1daec0e1aa294

> One final note: I could not find a reasonable explanation for why 
> opkg-tools require code changes to support a different compressor. BSD 
> tar and GNU tar both can easily accept compressors that they have no 
> idea about (via -I option) because all of them provide a unified 
> command line interface for use in pipes. If this were done similar to 
> tar, we could have used any compressor we wanted, including the 
> multithreaded versions (zstdmt)

Well, presumably IPK creation tools can only support the matrix of 
compression algorithms which your opkg binary can decompress. I suppose 
someone could try to implement a plugable compression module system for 
opkg. But given that nearly everyone uses opkg in an embedded context, 
I'm not sure it would get much use.

>
> On Tue, Sep 13, 2022 at 12:43 PM Khem Raj <raj.khem@gmail.com> wrote:
>
>     On Tue, Sep 13, 2022 at 12:19 PM Alex Stewart
>     <alex.stewart@ni.com> wrote:
>     >
>     > ACK from me - apart from enabling zstd by default.
>     >
>     > On 9/13/22 07:37, Etienne Cordonnier via lists.openembedded.org
>     <https://urldefense.com/v3/__http://lists.openembedded.org__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_bxrNjvo$>
>     wrote:
>     > > This allows the use of zstd for opkg packages by using
>     OPKGBUILDCMD:
>     > > OPKGBUILDCMD = "opkg-build -Z zstd"
>     > >
>     > > Signed-off-by: Alex Feinman <afeinman@snap.com>
>     > > Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
>     > > ---
>     > >   meta/recipes-devtools/opkg/opkg_0.6.0.bb
>     <https://urldefense.com/v3/__http://opkg_0.6.0.bb__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_-65pBFo$>
>     | 3 ++-
>     > >   1 file changed, 2 insertions(+), 1 deletion(-)
>     > >
>     > > diff --git a/meta/recipes-devtools/opkg/opkg_0.6.0.bb
>     <https://urldefense.com/v3/__http://opkg_0.6.0.bb__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_-65pBFo$>
>     b/meta/recipes-devtools/opkg/opkg_0.6.0.bb
>     <https://urldefense.com/v3/__http://opkg_0.6.0.bb__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_-65pBFo$>
>     > > index 7b351e8123..e38d9d6f3f 100644
>     > > --- a/meta/recipes-devtools/opkg/opkg_0.6.0.bb
>     <https://urldefense.com/v3/__http://opkg_0.6.0.bb__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_-65pBFo$>
>     > > +++ b/meta/recipes-devtools/opkg/opkg_0.6.0.bb
>     <https://urldefense.com/v3/__http://opkg_0.6.0.bb__;!!FbZ0ZwI3Qg!u0KgIth5yNSO1tok49C5_xo0QPHIFLa4kZBl3vVZwB-2Ui1uYBW7nt85fKXXM_VAHZ2LdFx_-65pBFo$>
>     > > @@ -30,7 +30,7 @@ inherit autotools pkgconfig ptest
>     > >   target_localstatedir := "${localstatedir}"
>     > >   OPKGLIBDIR ??= "${target_localstatedir}/lib"
>     > >
>     > > -PACKAGECONFIG ??= "libsolv"
>     > > +PACKAGECONFIG ??= "libsolv zstd"
>     >
>     > Building in zstd support by default is a little suspect to me.
>     >
>     > Unless I'm mistaken, OE-core will only build xz-compressed IPKs by
>     > default. So zstd support would be unnecessary for a distro
>     integrator
>     > who just uses upstream OE-core.
>     >
>     > For distros which use zstd compression in their packages, I think it
>     > would be more appropriate to overwrite the opkg PACKAGECONFIG in a
>     > .bbappend.
>     >
>
>     This is perhaps fine. I do wonder if there is some performance
>     comparison data between xz and zstd compressed ipks
>     with opkg, it might help users on making this choice and also if we
>     should consider using
>     zstd by default at some point or not.
>
>     > Is there something I'm not considering here?
>     >
>     > >
>     > >   PACKAGECONFIG[gpg] = "--enable-gpg,--disable-gpg,\
>     > >       gnupg gpgme libgpg-error,\
>     > > @@ -39,6 +39,7 @@ PACKAGECONFIG[gpg] =
>     "--enable-gpg,--disable-gpg,\
>     > >   PACKAGECONFIG[curl] = "--enable-curl,--disable-curl,curl"
>     > >   PACKAGECONFIG[ssl-curl] =
>     "--enable-ssl-curl,--disable-ssl-curl,curl openssl"
>     > >   PACKAGECONFIG[sha256] = "--enable-sha256,--disable-sha256"
>     > > +PACKAGECONFIG[zstd] = "--enable-zstd,--disable-zstd,zstd"
>     > >   PACKAGECONFIG[libsolv] =
>     "--with-libsolv,--without-libsolv,libsolv"
>     > >
>     > >   EXTRA_OECONF:class-native =
>     "--localstatedir=/${@os.path.relpath('${localstatedir}',
>     '${STAGING_DIR_NATIVE}')}
>     --sysconfdir=/${@os.path.relpath('${sysconfdir}',
>     '${STAGING_DIR_NATIVE}')}"
>     > >
>     > >
>     > >
>     >
>     > --
>     > Alex Stewart
>     > Software Engineer - NI Real-Time OS
>     > NI (National Instruments)
>     >
>     > alex.stewart@ni.com
>     >
>     >
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-- 
Alex Stewart
Software Engineer - NI Real-Time OS
NI (National Instruments)

alex.stewart@ni.com