On Wed, Oct 12, 2016 at 2:38 PM, Junio C Hamano <gits...@pobox.com> wrote: > Johannes Sixt <j...@kdbg.org> writes: > >> Sigh. DCLP, the Double Checked Locking Pattern. ... >> I suggest you go without it, then measure, and only *then* optimize if >> it is a bottleneck. > > That comes from me in earlier discussion before the patch, namely in > <xmqqeg3m8y6y....@gitster.mtv.corp.google.com>, where I wondered if > a cheap check outside the lock may be a possible optimization > opportunity, as this is a classic singleton that will not be > deinitialized, and once the codepath gets exercised, we would be > taking the "nothing to do" route 100% of the time. >
Having followed that advice (and internally having a DCLP), I think we have Triple Checked Locking Pattern in this patch. Nobody wrote a paper on how that would not work, yet. ;) In the reroll I plan to reduce it to a Single Checked (inside a mutex) Locking Pattern, though I would expect that performance (or lack thereof) will show then. But let's postpone measuring until we have a working patch.
