On Wed, Sep 18, 2019 at 6:57 PM Tom Seewald <tseewald(a)gmail.com> wrote:
Hi Chris,
Does zswap actually keep the data compressed when the DRAM-based swap is full, and it
writes to the spill-over non-volatile swap device?
I'm not an expert on this at all, however my understanding was that zswap must
decompress the data before it writes to the backing swap. But perhaps I am
misunderstanding the purpose of zswap_writeback_entry()[1] and/or what it does.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/m...
I don't know. But based on the tests I mention upthread, I'm not sure
how uncompressed pages are being swapped to disk. But then those times
don't account for even a 2:1 compression ratio, which is the best that
zbud/lz4 can achieve.
--
Chris Murphy