On Mon, Aug 07, 2023 at 09:29:08AM -0300, Tulio Magno Quites Machado Filho wrote: > "Richard W.M. Jones" <rjones@xxxxxxxxxx> writes: > > > The background to this is I've spent far too long trying to optimize > > the conversion of qcow2 files to raw files. Most existing qcow2 files > > that you can find online are zlib compressed, including the qcow2 > > images provided by Fedora. Each cluster in the file is separately > > compressed as a zlib stream, and qemu uses zlib library functions to > > decompress them. When downloading and decompressing these files, I > > measured 40%+ of the total CPU time is doing zlib decompression. > > This number may go even higher on s390x [1] because zlib-ng supports > hardware acceleration. > > qatzip [2] and libnxz [3] should provide performance on the same order of > magnitude for Intel and Power9 processors, with the negative side of not > using a single library. > > > We already package zlib-ng in Fedora: > > > > https://src.fedoraproject.org/rpms/zlib-ng/blob/rawhide/f/zlib-ng.spec > > https://github.com/zlib-ng/zlib-ng > > > > In my test zlib-ng is about 40% faster. > > > > Sadly zlib-ng is not compiled with the ZLIB_COMPAT option. What this > > means in practice is that the zlib functions have different names > > (eg. zng_inflateInit instead of inflateInit). It is not a drop-in > > replacement for zlib and software would need to be adjusted to use it. > > > > However there is this bug / RFE to package the compat library. > > > > https://bugzilla.redhat.com/show_bug.cgi?id=2145239 > > > > It literally replaces /usr/lib64/libz.so.1, so pretty high stakes. It > > has the appropriate Provides/Conflicts. > > > > Anyway, 40% (or whatever, but significant) performance improvement > > sounds good for a very widely used operation. > > > > So I'd like to ask Fedora ... > > > > What do we think about the opt in approach of adding a patch similar > > to the one proposed in bug 2145239, where I think you could "simply" > > install zlib-ng to get better performance with existing software? > > ("simply" because it seems high risk of going wrong) > > Wearing my zlib-ng fedora maintainer hat: > I like the idea of this patch, although I think it needs a few changes. > I'd like to merge it and add another package with the same source code, > but different value for compat, i.e. package zlib-ng would still > distribute the zlib-ng API while the new package would distribute the > zlib-compatible API. Would it help with maintenance, security issues etc. if we keep a single package, and simply perform the build twice? e.g. ncurses does this: https://src.fedoraproject.org/rpms/ncurses/blob/rawhide/f/ncurses.spec#_145-165 Best regards, -- Michel Alexandre Salim identities: https://keyoxide.org/5dce2e7e9c3b1cffd335c1d78b229d2f7ccc04f2
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