After taking a look at the call trace during a truncate that extends a
file, eCryptfs could probably handle this in a more efficient way.
-> ecryptfs_setattr
-> ecryptfs_truncate
-> ecryptfs_write
...
-> ecryptfs_get_locked_page
-> ecryptfs_readpage
-> ecryptfs_read_lower_page_segment
-> kmap
<- kmap
-> ecryptfs_read_lower
<- ecryptfs_read_lower
<- ecryptfs_read_lower_page_segment
<- ecryptfs_readpage
<- ecryptfs_get_locked_page
-> ecryptfs_encrypt_page
-> alloc_pages_node").call
<- alloc_pages_node").return
-> kmap
<- kmap
-> ecryptfs_encrypt_extent
-> ecryptfs_derive_iv
-> ecryptfs_calculate_md5
<- ecryptfs_calculate_md5
<- ecryptfs_derive_iv
<- ecryptfs_encrypt_extent
-> ecryptfs_write_lower
<- ecryptfs_write_lower
<- ecryptfs_encrypt_page
...
<- ecryptfs_write
<- ecryptfs_truncate
<- ecryptfs_setattr
I don't think there's any need for the ecryptfs_readpage ->
ecryptfs_read_lower_page_segment -> ecryptfs_read_lower sequence, as we
know that we just need to encrypt a bunch of zeroes. Fixing that will
improve performance, but the CPU is still likely to be pegged pretty
high while doing all the encryption operations.
Improving the truncate path would really be a nice-to-have improvement,
but I will probably not be able to devote much time to it. If someone
wants to try to tackle it, I'll be more than happy to provide any help
that I can.
** Also affects: ecryptfs
Importance: Undecided
Status: New
** Changed in: ecryptfs
Status: New => Triaged
** Changed in: ecryptfs
Importance: Undecided => Low
** Changed in: ecryptfs
Importance: Low => Wishlist
--
downloading a torrent to an encrypted home partition hangs and uses 100% CPU
https://bugs.launchpad.net/bugs/431975
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