Seahub caches items (avatars, profiles, etc) on the file system in /tmp/seahub_cache/ by default. You can replace it with Memcached. After installing python-memcached, add the following lines to seahub_settings.py.
CACHES = {
'default': {
'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
'LOCATION': '127.0.0.1:11211',
}
}