[tor-bugs] #22706 [Core Tor/Tor]: Compress cached descriptors and consensus

Tor Bug Tracker & Wiki blackhole at torproject.org
Fri Jun 23 13:19:39 UTC 2017


#22706: Compress cached descriptors and consensus
---------------------------------------+-----------------------------------
 Reporter:  nickm                      |          Owner:
     Type:  defect                     |         Status:  new
 Priority:  Medium                     |      Milestone:  Tor:
                                       |  0.3.2.x-final
Component:  Core Tor/Tor               |        Version:
 Severity:  Normal                     |     Resolution:
 Keywords:  sponsor8-maybe disk-usage  |  Actual Points:
Parent ID:  #7176                      |         Points:  4
 Reviewer:  nickm                      |        Sponsor:
---------------------------------------+-----------------------------------
Changes (by nickm):

 * status:  needs_review => new
 * keywords:  sponsor8-maybe disk-usage review-group-18 => sponsor8-maybe
     disk-usage


Comment:

 Review:
   * I think this presumes #22704.
   * This patch seems to have the same issue with anonymous mmaps as I
 noted in #22704: is it really saving RAM? I can believe it saves disk when
 Tor isn't running.
   * This patch should IMO be off-by-default, and I don't think it's safe
 to turn it on for directory caches.
   * The compression parts need to be rewritten to use the new compress.c
 APIs.
   * There are bigger memory savings available on clients: once we have the
 (micro)descriptors parsed, we can just leave them on disk, parse them, and
 not keep their text in memory at all. (After parsing we only use the text
 to answer controller requests and directory requests.)
   * We shouldn't add our own functions in the gz* namespace.
   * Cache compression won't work very well: it only handles one
 (micro)descriptor at a time.

 If we decide to take this approach, we should start with a fresh patch,
 using parts of the design here as needed.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22706#comment:2>
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