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authorGravatar Joey Hess <joey@kitenet.net>2013-09-22 19:45:08 -0400
committerGravatar Joey Hess <joey@kitenet.net>2013-09-22 20:06:02 -0400
commitca7695f9e746ef0d9cc70ffed6c2590dba29db79 (patch)
tree2291c29ab8d6126fea397fdd3d1e502cff064b1c /Backend
parent978d0362b0469236c848882df9b3a7d412fc96f9 (diff)
Use cryptohash rather than SHA for hashing.
This is a massive win on OSX, which doesn't have a sha256sum normally. Only use external hash commands when the file is > 1 mb, since cryptohash is quite close to them in speed. SHA is still used to calculate HMACs. I don't quite understand cryptohash's API for those. Used the following benchmark to arrive at the 1 mb number. 1 mb file: benchmarking sha256/internal mean: 13.86696 ms, lb 13.83010 ms, ub 13.93453 ms, ci 0.950 std dev: 249.3235 us, lb 162.0448 us, ub 458.1744 us, ci 0.950 found 5 outliers among 100 samples (5.0%) 4 (4.0%) high mild 1 (1.0%) high severe variance introduced by outliers: 10.415% variance is moderately inflated by outliers benchmarking sha256/external mean: 14.20670 ms, lb 14.17237 ms, ub 14.27004 ms, ci 0.950 std dev: 230.5448 us, lb 150.7310 us, ub 427.6068 us, ci 0.950 found 3 outliers among 100 samples (3.0%) 2 (2.0%) high mild 1 (1.0%) high severe 2 mb file: benchmarking sha256/internal mean: 26.44270 ms, lb 26.23701 ms, ub 26.63414 ms, ci 0.950 std dev: 1.012303 ms, lb 925.8921 us, ub 1.122267 ms, ci 0.950 variance introduced by outliers: 35.540% variance is moderately inflated by outliers benchmarking sha256/external mean: 26.84521 ms, lb 26.77644 ms, ub 26.91433 ms, ci 0.950 std dev: 347.7867 us, lb 210.6283 us, ub 571.3351 us, ci 0.950 found 6 outliers among 100 samples (6.0%) import Crypto.Hash import Data.ByteString.Lazy as L import Criterion.Main import Common testfile :: FilePath testfile = "/run/shm/data" -- on ram disk main = defaultMain [ bgroup "sha256" [ bench "internal" $ whnfIO internal , bench "external" $ whnfIO external ] ] sha256 :: L.ByteString -> Digest SHA256 sha256 = hashlazy internal :: IO String internal = show . sha256 <$> L.readFile testfile external :: IO String external = do s <- readProcess "sha256sum" [testfile] return $ fst $ separate (== ' ') s
Diffstat (limited to 'Backend')
-rw-r--r--Backend/SHA.hs18
1 files changed, 10 insertions, 8 deletions
diff --git a/Backend/SHA.hs b/Backend/SHA.hs
index a735ce1e5..7150a4202 100644
--- a/Backend/SHA.hs
+++ b/Backend/SHA.hs
@@ -1,6 +1,6 @@
{- git-annex SHA backends
-
- - Copyright 2011,2012 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
@@ -12,10 +12,10 @@ import qualified Annex
import Types.Backend
import Types.Key
import Types.KeySource
+import Utility.Hash
import Utility.ExternalSHA
import qualified Build.SysConfig as SysConfig
-import Data.Digest.Pure.SHA
import qualified Data.ByteString.Lazy as L
import Data.Char
@@ -70,12 +70,14 @@ shaCommand shasize filesize
| shasize == 512 = use SysConfig.sha512 sha512
| otherwise = error $ "bad sha size " ++ show shasize
where
- use Nothing sha = Left $ showDigest . sha
- use (Just c) sha
- {- use builtin, but slower sha for small files
- - benchmarking indicates it's faster up to
- - and slightly beyond 50 kb files -}
- | filesize < 51200 = use Nothing sha
+ use Nothing hasher = Left $ show . hasher
+ use (Just c) hasher
+ {- Use builtin, but slightly slower hashing for
+ - smallish files. Cryptohash benchmarks 90 to 101%
+ - faster than external hashers, depending on the hash
+ - and system. So there is no point forking an external
+ - process unless the file is large. -}
+ | filesize < 1048576 = use Nothing hasher
| otherwise = Right c
{- A key is a checksum of its contents. -}