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Re: [PATCH 2/2] upload-pack: reduce lock contention when writing packfile data

From
Patrick Steinhardt <ps@pks.im>
Date
Mar 3, 2026, 13:47 UTC
Message-ID
<aabmXF5D1rMRZgP3@pks.im>
In-Reply-To
<20260303133540.GA818878@coredump.intra.peff.net>
On Tue, Mar 03, 2026 at 08:35:40AM -0500, Jeff King wrote:
Show 17 quoted lines
> On Tue, Mar 03, 2026 at 10:31:46AM +0100, Patrick Steinhardt wrote:
> > We would likely hit this issue if we insist on the buffer being
> > completely filled before sending it out. But that's why I adapted the
> > logic to say that we send out once we've filled it at least 2/3rds of
> > the pktline limit. So in your case above we wouldn't face an issue as
> > we'd already send the first 50kB, as it is smaller than 2/3rds of the
> > maximum length (~42kB).
> > 
> > That being said, you'll still be able to construct cases where we have
> > weird edge cases. For example if you consistently send one byte less
> > than 2/3rds of the capacity.
> 
> Right, my numbers were just meant as examples. Whatever the values, it
> means that whatever is generating the pack data (pack-objects or
> otherwise) really wants to be in sync with how upload-pack is buffering.
> Or vice versa. If we just pass back whole chunks of what we read() in
> upload-pack, then that happens automatically.

Yeah, that's fair. I'll include this part in v2 for now so that we can discuss once the bigger picture emerges :)

Thanks!
Patrick
Previous: Jeff KingNext: Patrick Steinhardt
Message 12 of 53 in “upload-pack: reduce lock contention when writing packfile data”
  1. 0/2 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Feb 27, 2026
  2. 1/2 upload-pack: fix debug statement when flushing packfile dataPatrick Steinhardt, Feb 27, 2026
  3. 2/2 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Feb 27, 2026
  4. brian m. carlsonFeb 27, 2026
  5. Patrick SteinhardtFeb 27, 2026
  6. Junio C HamanoFeb 27, 2026
  7. Jeff KingFeb 27, 2026
  8. Patrick SteinhardtMar 2, 2026
  9. Jeff KingMar 2, 2026
  10. Patrick SteinhardtMar 3, 2026
  11. Jeff KingMar 3, 2026
  12. Patrick SteinhardtMar 3, 2026
  13. 00/10 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 3, 2026
  14. 01/10 upload-pack: fix debug statement when flushing packfile dataPatrick Steinhardt, Mar 3, 2026
  15. 02/10 upload-pack: adapt keepalives based on bufferingPatrick Steinhardt, Mar 3, 2026
  16. Jeff KingMar 5, 2026
  17. Patrick SteinhardtMar 10, 2026
  18. 03/10 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 3, 2026
  19. Jeff KingMar 5, 2026
  20. Patrick SteinhardtMar 10, 2026
  21. 04/10 git-compat-util: introduce `cast_size_t_to_ssize_t()`Patrick Steinhardt, Mar 3, 2026
  22. 05/10 compat/posix: introduce writev(3p) wrapperPatrick Steinhardt, Mar 3, 2026
  23. Junio C HamanoMar 4, 2026
  24. Jeff KingMar 5, 2026
  25. brian m. carlsonMar 5, 2026
  26. Johannes SixtMar 5, 2026
  27. brian m. carlsonMar 5, 2026
  28. Patrick SteinhardtMar 10, 2026
  29. 06/10 wrapper: introduce writev(3p) wrappersPatrick Steinhardt, Mar 3, 2026
  30. 07/10 sideband: use writev(3p) to send pktlinesPatrick Steinhardt, Mar 3, 2026
  31. Junio C HamanoMar 4, 2026
  32. 08/10 csum-file: introduce `hashfd_ext()`Patrick Steinhardt, Mar 3, 2026
  33. Junio C HamanoMar 4, 2026
  34. Patrick SteinhardtMar 10, 2026
  35. 09/10 csum-file: drop `hashfd_throughput()`Patrick Steinhardt, Mar 3, 2026
  36. 10/10 builtin/pack-objects: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 3, 2026
  37. 00/10 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 10, 2026
  38. 01/10 upload-pack: fix debug statement when flushing packfile dataPatrick Steinhardt, Mar 10, 2026
  39. 02/10 upload-pack: adapt keepalives based on bufferingPatrick Steinhardt, Mar 10, 2026
  40. 03/10 upload-pack: prefer flushing data over sending keepalivePatrick Steinhardt, Mar 10, 2026
  41. Junio C HamanoMar 10, 2026
  42. Patrick SteinhardtMar 10, 2026
  43. 04/10 upload-pack: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 10, 2026
  44. 05/10 compat/posix: introduce writev(3p) wrapperPatrick Steinhardt, Mar 10, 2026
  45. Junio C HamanoMar 10, 2026
  46. 06/10 wrapper: introduce writev(3p) wrappersPatrick Steinhardt, Mar 10, 2026
  47. 07/10 sideband: use writev(3p) to send pktlinesPatrick Steinhardt, Mar 10, 2026
  48. 08/10 csum-file: introduce `hashfd_ext()`Patrick Steinhardt, Mar 10, 2026
  49. 09/10 csum-file: drop `hashfd_throughput()`Patrick Steinhardt, Mar 10, 2026
  50. 10/10 builtin/pack-objects: reduce lock contention when writing packfile dataPatrick Steinhardt, Mar 10, 2026
  51. Junio C HamanoMar 10, 2026
  52. Johannes SixtMar 10, 2026
  53. Patrick SteinhardtMar 11, 2026

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