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Re: [PATCH 6/6] fetch: avoid second connectivity check if we already have all objects

From
Patrick Steinhardt <ps@pks.im>
Date
Aug 23, 2021, 06:52 UTC
Message-ID
<YSNFx9FdSWOy6b45@ncase>
In-Reply-To
<1d5ae688-fa08-6c8c-345f-9b0389e21dd7@gmail.com>
On Fri, Aug 20, 2021 at 10:47:11AM -0400, Derrick Stolee wrote:
Show 23 quoted lines
> On 8/20/2021 6:08 AM, Patrick Steinhardt wrote:
> > When fetching refs, we are doing two connectivity checks:
> > 
> >     - The first one in `fetch_refs()` is done such that we can
> >       short-circuit the case where we already have all objects
> >       referenced by the updated set of refs.
> > 
> >     - The second one in `store_updated_refs()` does a sanity check that
> >       we have all objects after we have fetched the packfile.
> > 
> > We always execute both connectivity checks, but this is wasteful in case
> > the first connectivity check already notices that we have all objects
> > locally available.
> > 
> > Refactor the code to do both connectivity checks in `fetch_refs()`,
> > which allows us to easily skip the second connectivity check if we
> > already have all objects available. This refactoring is safe to do given
> > that we always call `fetch_refs()` followed by `consume_refs()`, which
> > is the only caller of `store_updated_refs()`.
> 
> Should we try to make it more clear that fetch_refs() must be followed
> by consume_refs() via a comment above the fetch_refs(), or possibly even
> its call sites?

I wasn't quite happy with this outcome, either. How about we instead merge both functions into `fetch_and_consume_refs()`? Both are quite short, and that makes sure we always call them together to make the requirement explicit.

I'll add another patch to do this refactoring.
Patrick
Previous: Derrick StoleeNext: Derrick Stolee
Message 20 of 48 in “Speed up mirror-fetches with many refs”
  1. 0/6 Speed up mirror-fetches with many refsPatrick Steinhardt, Aug 20, 2021
  2. 1/6 fetch: speed up lookup of want refs via commit-graphPatrick Steinhardt, Aug 20, 2021
  3. Derrick StoleeAug 20, 2021
  4. Junio C HamanoAug 20, 2021
  5. Patrick SteinhardtAug 23, 2021
  6. Derrick StoleeAug 25, 2021
  7. 2/6 fetch: avoid unpacking headers in object existence checkPatrick Steinhardt, Aug 20, 2021
  8. Ævar Arnfjörð BjarmasonAug 25, 2021
  9. 3/6 connected: refactor iterator to return next object ID directlyPatrick Steinhardt, Aug 20, 2021
  10. Derrick StoleeAug 20, 2021
  11. Junio C HamanoAug 20, 2021
  12. René ScharfeAug 20, 2021
  13. Patrick SteinhardtAug 23, 2021
  14. 4/6 fetch-pack: optimize loading of refs via commit graphPatrick Steinhardt, Aug 20, 2021
  15. Derrick StoleeAug 20, 2021
  16. 5/6 fetch: refactor fetch refs to be more extendablePatrick Steinhardt, Aug 20, 2021
  17. Derrick StoleeAug 20, 2021
  18. 6/6 fetch: avoid second connectivity check if we already have all objectsPatrick Steinhardt, Aug 20, 2021
  19. Derrick StoleeAug 20, 2021
  20. Patrick SteinhardtAug 23, 2021
  21. Derrick StoleeAug 20, 2021
  22. Junio C HamanoAug 21, 2021
  23. 0/7 Speed up mirror-fetches with many refsPatrick Steinhardt, Aug 24, 2021
  24. 1/7 fetch: speed up lookup of want refs via commit-graphPatrick Steinhardt, Aug 24, 2021
  25. Derrick StoleeAug 25, 2021
  26. 2/7 fetch: avoid unpacking headers in object existence checkPatrick Steinhardt, Aug 24, 2021
  27. 3/7 connected: refactor iterator to return next object ID directlyPatrick Steinhardt, Aug 24, 2021
  28. 4/7 fetch-pack: optimize loading of refs via commit graphPatrick Steinhardt, Aug 24, 2021
  29. 5/7 fetch: refactor fetch refs to be more extendablePatrick Steinhardt, Aug 24, 2021
  30. Derrick StoleeAug 25, 2021
  31. Patrick SteinhardtSep 1, 2021
  32. 7/7 fetch: avoid second connectivity check if we already have all objectsPatrick Steinhardt, Aug 24, 2021
  33. 6/7 fetch: merge fetching and consuming refsPatrick Steinhardt, Aug 24, 2021
  34. Derrick StoleeAug 25, 2021
  35. Patrick SteinhardtSep 1, 2021
  36. Junio C HamanoAug 24, 2021
  37. Patrick SteinhardtAug 25, 2021
  38. Derrick StoleeAug 25, 2021
  39. 0/7 Speed up mirror-fetches with many refsPatrick Steinhardt, Sep 1, 2021
  40. 1/7 fetch: speed up lookup of want refs via commit-graphPatrick Steinhardt, Sep 1, 2021
  41. 2/7 fetch: avoid unpacking headers in object existence checkPatrick Steinhardt, Sep 1, 2021
  42. 3/7 connected: refactor iterator to return next object ID directlyPatrick Steinhardt, Sep 1, 2021
  43. 4/7 fetch-pack: optimize loading of refs via commit graphPatrick Steinhardt, Sep 1, 2021
  44. 5/7 fetch: refactor fetch refs to be more extendablePatrick Steinhardt, Sep 1, 2021
  45. 6/7 fetch: merge fetching and consuming refsPatrick Steinhardt, Sep 1, 2021
  46. 7/7 fetch: avoid second connectivity check if we already have all objectsPatrick Steinhardt, Sep 1, 2021
  47. Junio C HamanoSep 1, 2021
  48. Junio C HamanoSep 8, 2021

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