diff --git a/src/bitrot.py b/src/bitrot.py
index bd51228..e75475f 100644
--- a/src/bitrot.py
+++ b/src/bitrot.py
@@ -30,6 +30,7 @@ import argparse
 import atexit
 import datetime
 import errno
+import functools
 import hashlib
 import os
 import shutil
@@ -37,22 +38,28 @@ import sqlite3
 import stat
 import sys
 import tempfile
+import time
 
 
-CHUNK_SIZE = 16384
+DEFAULT_CHUNK_SIZE = 16384
 DOT_THRESHOLD = 200
 VERSION = (0, 5, 1)
 
 
-def sha1(path):
+def sha1(path, chunk_size):
     digest = hashlib.sha1()
     with open(path) as f:
-        d = f.read(CHUNK_SIZE)
+        d = f.read(chunk_size)
         while d:
             digest.update(d)
-            d = f.read(CHUNK_SIZE)
+            d = f.read(chunk_size)
     return digest.hexdigest()
 
+def throttled_commit(conn, commit_interval, last_commit_time):
+    if time.time() - last_commit_time > commit_interval:
+        conn.commit()
+        return time.time()
+    return last_commit_time
 
 def get_sqlite3_cursor(path, copy=False):
     if copy:
@@ -80,7 +87,7 @@ def get_sqlite3_cursor(path, copy=False):
     return conn
 
 
-def run(verbosity=1, test=False):
+def run(verbosity=1, test=False, commit_interval=300, chunk_size=DEFAULT_CHUNK_SIZE):
     current_dir = b'.'   # sic, relative path
     bitrot_db = os.path.join(current_dir, b'.bitrot.db')
     conn = get_sqlite3_cursor(bitrot_db, copy=test)
@@ -113,6 +120,8 @@ def run(verbosity=1, test=False):
                 paths.append(p)
                 total_size += st.st_size
     paths.sort()
+    last_commit_time = 0
+    tcommit = functools.partial(throttled_commit, conn, commit_interval)
     for p in paths:
         st = os.stat(p)
         new_mtime = int(st.st_mtime)
@@ -123,7 +132,7 @@ def run(verbosity=1, test=False):
                 sys.stdout.write(size_fmt)
                 sys.stdout.flush()
                 last_reported_size = size_fmt
-        new_sha1 = sha1(p)
+        new_sha1 = sha1(p, chunk_size)
         update_ts = datetime.datetime.utcnow().strftime(
             '%Y-%m-%d %H:%M:%S%z'
         )
@@ -144,13 +153,14 @@ def run(verbosity=1, test=False):
                     cur.execute('UPDATE bitrot SET mtime=?, path=?, '
                                 'timestamp=? WHERE hash=?',
                                 (new_mtime, p_uni, update_ts, new_sha1))
-                    conn.commit()
+
+                    last_commit_time = tcommit(last_commit_time)
                     break
             else:
                 new_paths.append(p)
                 cur.execute('INSERT INTO bitrot VALUES (?, ?, ?, ?)',
                     (p_uni, new_mtime, new_sha1, update_ts))
-                conn.commit()
+                last_commit_time = tcommit(last_commit_time)
             continue
         stored_mtime, stored_sha1, update_ts = row
         if int(stored_mtime) != new_mtime:
@@ -158,7 +168,7 @@ def run(verbosity=1, test=False):
             cur.execute('UPDATE bitrot SET mtime=?, hash=?, timestamp=? '
                         'WHERE path=?',
                         (new_mtime, new_sha1, update_ts, p_uni))
-            conn.commit()
+            last_commit_time = tcommit(last_commit_time)
         elif stored_sha1 != new_sha1:
             error_count += 1
             print('\rerror: SHA1 mismatch for {}: expected {}, got {}.'
@@ -169,7 +179,8 @@ def run(verbosity=1, test=False):
             )
     for path in missing_paths:
         cur.execute('DELETE FROM bitrot WHERE path=?', (path,))
-        conn.commit()
+        last_commit_time = tcommit(last_commit_time)
+    conn.commit()
     cur.execute('SELECT COUNT(path) FROM bitrot')
     all_count = cur.fetchone()[0]
     if verbosity:
@@ -238,6 +249,10 @@ def run_from_command_line():
         help='just test against an existing database, don\'t update anything')
     parser.add_argument('--version', action='version',
         version='%(prog)s {}.{}.{}'.format(*VERSION))
+    parser.add_argument('--commit-interval', type=float, default=300,
+        help='min time between commits (0 commits on every operation)')
+    parser.add_argument('--chunk-size', type=int, default=DEFAULT_CHUNK_SIZE,
+        help='read files this many bytes at a time')
     args = parser.parse_args()
     if args.sum:
         try:
@@ -250,7 +265,9 @@ def run_from_command_line():
             verbosity = 0
         elif args.verbose:
             verbosity = 2
-        run(verbosity=verbosity, test=args.test)
+        run(verbosity=verbosity, test=args.test,
+            commit_interval=args.commit_interval,
+            chunk_size=args.chunk_size)
 
 
 if __name__ == '__main__':