git: 89d5cbb82294 - main - libnv: optimize nvlist size calculation

[Mariusz Zaborski]

No, I will do this till end of the week.

Thanks,
Mariusz

On Mon, 14 Jun 2021 at 14:10, Kristof Provost <kristof at sigsegv.be> wrote:

> On 11 Jun 2021, at 17:51, Mariusz Zaborski wrote:
> > The branch main has been updated by oshogbo:
> >
> > URL:
> >
> https://cgit.FreeBSD.org/src/commit/?id=89d5cbb82294c8624e66f920d50353057ccab14b
> >
> > commit 89d5cbb82294c8624e66f920d50353057ccab14b
> > Author:     Mariusz Zaborski <oshogbo at FreeBSD.org>
> > AuthorDate: 2021-06-11 15:35:36 +0000
> > Commit:     Mariusz Zaborski <oshogbo at FreeBSD.org>
> > CommitDate: 2021-06-11 15:51:29 +0000
> >
> >     libnv: optimize nvlist size calculation
> >
> >     If we had a multiple nvlist, during nvlist_pack, we calculated the
> > size
> >     of every nvlist separately. For example, if we had a nvlist with
> > three
> >     nodes each containing another (A contains B, and B contains C), we
> > first
> >     calculated the size of nvlist A (which contains B, C), then we
> > calculate
> >     the size of B (which contains C, notice that we already did the
> >     calculation of B, when we calculate A), and finally C. This means
> > that
> >     this calculation was O(N!). This was done because each time we
> > pack
> >     nvlist, we have to put its size in the header
> >     (the separate header for A, B, and C).
> >
> >     To not break the ABI and to reduce the complexity of nvlist_size,
> >     instead of calculating the nvlist size when requested,
> >     we track the size of each nvlist.
> >
> >     Reported by:    pjd, kp
> >     Tested by:      kp
>
> Thanks for this!
>
> Do you object to this being MFCd in a few days?
>
> Thanks,
> Kristof
>