From: Brian Warner Date: Thu, 14 Feb 2008 00:41:20 +0000 (-0700) Subject: mutable.py: add comments to justify initial-read size choices X-Git-Tag: allmydata-tahoe-0.8.0~60 X-Git-Url: https://git.rkrishnan.org/pf/content/en/footer/FOOURL?a=commitdiff_plain;h=85eae2bf57002a04d18159e5564d565391f41fe7;p=tahoe-lafs%2Ftahoe-lafs.git mutable.py: add comments to justify initial-read size choices --- diff --git a/src/allmydata/mutable.py b/src/allmydata/mutable.py index b125f2f0..01b6f5f9 100644 --- a/src/allmydata/mutable.py +++ b/src/allmydata/mutable.py @@ -261,6 +261,12 @@ class Retrieve: # remove that share from the sharemap. and start step#6 again. initial_query_count = 5 + # how much data should be read on the first fetch? It would be nice + # if we could grab small directories in a single RTT. The way we pack + # dirnodes consumes about 112 bytes per child. The way we pack + # mutable files puts about 935 bytes of pubkey+sig+hashes, then our + # data, then about 1216 bytes of encprivkey. So 2kB ought to get us + # about 9 entries, which seems like a good default. self._read_size = 2000 # we might not know how many shares we need yet. @@ -774,8 +780,10 @@ class Publish: # the privkey from somebody, which means reading more like 3KB, but # the code in _obtain_privkey will ensure that we manage that even if # we need an extra roundtrip. TODO: arrange to read 3KB from one peer - # who is likely to hold a share (like, say, ourselves), so we can - # avoid the latency of that extra roundtrip. + # who is likely to hold a share, so we can avoid the latency of that + # extra roundtrip. 3KB would get us the encprivkey from a dirnode + # with up to 7 entries, allowing us to make an update in 2 RTT + # instead of 3. self._read_size = 1000 d = defer.succeed(total_shares)