git/list[1] front-page[2] threads[3] people[4] search[5] about
 

Re: remove_duplicates() in builtin/fetch-pack.c is O(N^2)

From
MFMartin Fick <mfick@codeaurora.org>
Date
May 25, 2012, 00:54 UTC
Message-ID
<201205241854.56934.mfick@codeaurora.org>
In-Reply-To
<20120525003920.GB11300@sigill.intra.peff.net>
On Thursday, May 24, 2012 06:39:20 pm Jeff King wrote:
> On Thu, May 24, 2012 at 06:17:45PM -0600, Martin Fick 
wrote:
Show 9 quoted lines
> > Were your tests mostly warm cache tests?
> 
> Yes, exclusively warm. And all of the refs were packed,
> which makes the warm/cold difference less interesting
> (it's one 30MB or so file).  I don't think there's much
> point in thinking about the performance of 400K loose
> refs (which would be absolutely horrific cold-cache on
> most traditional filesystems). If you have that many,
> you would want to keep the bulk of them packed.
Mostly true, except for one strange case still I think?

When cloning a gerrit repo, users to not get the changes since they are not under refs/heads but refs/changes. So later, if they choose to fetch refs/changes/*, all of those new incoming refs are loose. Yes, someone should pack those refs right away, but I think it actually churns the hell out of my disk and takes a significant amount of time during the initial fetch. I am not certain about this, and the behavior may depend on the filesystem in use, but I think that this time might even be asynchronous (journals and all), it feels like my disk keeps churning for a while even after this is over. I believe that this might still be the worst case left with refs, and it can be pretty bad,

-Martin
-- 
Employee of Qualcomm Innovation Center, Inc. which is a 
member of Code Aurora Forum
Previous: Jeff KingNext: Jeff King
Message 26 of 46 in “remove_duplicates() in builtin/fetch-pack.c is O(N^2)”
  1. Michael HaggertyMay 21, 2012
  2. Junio C HamanoMay 21, 2012
  3. demerphqMay 21, 2012
  4. Jeff KingMay 21, 2012
  5. Jeff KingMay 21, 2012
  6. 1/5 fetch-pack: sort incoming headsJeff King, May 21, 2012
  7. Junio C HamanoMay 22, 2012
  8. Jeff KingMay 22, 2012
  9. Jeff KingMay 24, 2012
  10. 2/5 fetch-pack: avoid quadratic behavior in remove_duplicatesJeff King, May 21, 2012
  11. 3/5 add sorting infrastructure for list refsJeff King, May 21, 2012
  12. 4/5 fetch-pack: sort the list of incoming refsJeff King, May 21, 2012
  13. 5/5 fetch-pack: avoid quadratic loop in filter_refsJeff King, May 21, 2012
  14. Junio C HamanoMay 22, 2012
  15. Jeff KingMay 21, 2012
  16. Jeff KingMay 22, 2012
  17. Michael HaggertyMay 22, 2012
  18. Jeff KingMay 22, 2012
  19. Michael HaggertyMay 22, 2012
  20. Jeff KingMay 22, 2012
  21. Michael HaggertyMay 22, 2012
  22. Jeff KingMay 22, 2012
  23. Michael HaggertyMay 24, 2012
  24. Martin FickMay 25, 2012
  25. Jeff KingMay 25, 2012
  26. Martin FickMay 25, 2012
  27. Jeff KingMay 25, 2012
  28. Martin FickMay 25, 2012
  29. Jeff KingMay 25, 2012
  30. Nguyen Thai Ngoc DuyMay 22, 2012
  31. Michael HaggertyMay 22, 2012
  32. Jeff KingMay 22, 2012
  33. Junio C HamanoMay 22, 2012
  34. Jeff KingMay 22, 2012
  35. Michael HaggertyMay 24, 2012
  36. Nguyen Thai Ngoc DuyMay 23, 2012
  37. Junio C HamanoMay 22, 2012
  38. Martin FickMay 21, 2012
  39. Jeff KingMay 21, 2012
  40. Junio C HamanoMay 21, 2012
  41. Jeff KingMay 21, 2012
  42. Martin FickMay 22, 2012
  43. Jeff KingMay 22, 2012
  44. Martin FickMay 22, 2012
  45. Junio C HamanoMay 22, 2012
  46. Martin FickMay 23, 2012

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.