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docs: fix several imprecise or inaccurate values in performance.rst

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add cpu values for each operation
sort the list of values into the same order in each operation
refs #1398
This commit is contained in:
Zooko O'Whielacronx 2011-05-08 05:42:28 -07:00
parent 3dc491758d
commit 587e31a8cf
1 changed files with 36 additions and 19 deletions
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55
docs/performance.rst
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@ -47,7 +47,7 @@ cpu: ~A
network: ~N
memory footprint: N/K*S
memory footprint: S
when the file is not already uploaded
-------------------------------------
@ -62,19 +62,19 @@ disk: 2*A
cpu: 2*~A
network: ~N + ~A
network: N/K*A
memory footprint: N/K*S
Publishing an ``A``-byte mutable file
=====================================
cpu: ~A + a large constant for RSA keypair generation
network: A
memory footprint: N/K*A
cpu: ~A + a large constant for RSA keypair generation
notes: Tahoe-LAFS generates a new RSA keypair for each mutable file that it
publishes to a grid. This takes up to 1 or 2 seconds on a typical desktop PC.
@ -86,9 +86,9 @@ files, this may cause Tahoe-LAFS to have an unacceptably large memory footprint
Downloading ``B`` bytes of an ``A``-byte immutable file
=======================================================
network: B
cpu: ~B
cpu: ~A
network: B
notes: When Tahoe-LAFS 1.8.0 or later is asked to read an arbitrary
range of an immutable file, only the S-byte segments that overlap the
@ -101,6 +101,8 @@ the rest of the file even after the request was satisfied.)
Downloading ``B`` bytes of an ``A``-byte mutable file
=====================================================
cpu: ~A
network: A
memory footprint: A
@ -112,6 +114,8 @@ exploring fixes for this; see ticket #393 for more information.
Modifying ``B`` bytes of an ``A``-byte mutable file
===================================================
cpu: ~A
network: A
memory footprint: N/K*A
@ -127,6 +131,8 @@ the existing RSA keypair instead of generating a new one.
Inserting/Removing ``B`` bytes in an ``A``-byte mutable file
============================================================
cpu: ~A
network: A
memory footprint: N/K*A
@ -144,9 +150,11 @@ file".
Adding an entry to an ``A``-entry directory
===========================================
cpu: ~A
network: ~A
memory footprint: N/K*A
memory footprint: N/K*~A
notes: In Tahoe-LAFS, directories are implemented as specialized mutable
files. So adding an entry to a directory is essentially adding B
@ -155,9 +163,11 @@ files. So adding an entry to a directory is essentially adding B
Listing an ``A`` entry directory
================================
cpu: ~A
network: ~A
memory footprint: N/K*A
memory footprint: N/K*~A
notes: Listing a directory requires that the mutable file storing the
directory be downloaded from the grid. So listing an A entry
@ -167,7 +177,9 @@ file, since each directory entry is about 300-330 bytes in size.
Performing a file-check on an ``A``-byte file
=============================================
network: ~G, where G is the number of servers on your grid
cpu: ~G
network: ~G
memory footprint: negligible
@ -179,24 +191,29 @@ and repair operations.
Performing a file-verify on an ``A``-byte file
==============================================
cpu: ~N/K*A
network: N/K*A
memory footprint: N/K*S
notes: To verify a file, Tahoe-LAFS downloads all of the ciphertext
shares that were originally uploaded to the grid and integrity
checks them. This is, for well-behaved grids, likely to be more
expensive than downloading an A-byte file, since only a fraction
of these shares are necessary to recover the file.
shares that were originally uploaded to the grid and integrity checks
them. This is (for well-behaved grids) more expensive than downloading
an A-byte file, since only a fraction of these shares are necessary to
recover the file.
Repairing an ``A``-byte file (mutable or immutable)
===================================================
network: variable; up to around ~A
cpu: variable, between ~A and ~N/K*A
memory footprint: from S to (1+N/K)*S
network: variable; between A and N/K*A
notes: To repair a file, Tahoe-LAFS downloads the file, and generates/uploads
missing shares in the same way as when it initially uploads the file.
So, depending on how many shares are missing, this can be about as
expensive as initially uploading the file in the first place.
memory footprint: (1+N/K)*S
notes: To repair a file, Tahoe-LAFS downloads the file, and
generates/uploads missing shares in the same way as when it initially
uploads the file. So, depending on how many shares are missing, this
can cost as little as a download or as much as a download followed by
a full upload.