On 02/01/2013 09:31 AM, Seth Jennings wrote: > On 01/31/2013 08:38 PM, Minchan Kim wrote: >> On Thu, Jan 31, 2013 at 01:06:46PM -0600, Seth Jennings wrote: >>> On 01/31/2013 01:07 AM, Minchan Kim wrote: >>>> On Tue, Jan 29, 2013 at 03:40:23PM -0600, Seth Jennings wrote: >>>>> zswap is a thin compression backend for frontswap. It receives >>>>> pages from frontswap and attempts to store them in a compressed >>>>> memory pool, resulting in an effective partial memory reclaim and >>>>> dramatically reduced swap device I/O. >>>>> >>>>> Additionally, in most cases, pages can be retrieved from this >>>>> compressed store much more quickly than reading from tradition >>>>> swap devices resulting in faster performance for many workloads. >>>>> >>>>> This patch adds the zswap driver to mm/ >>>>> >>>>> Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> >>>>> --- >>>>> mm/Kconfig | 15 ++ >>>>> mm/Makefile | 1 + >>>>> mm/zswap.c | 656 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>>> 3 files changed, 672 insertions(+) >>>>> create mode 100644 mm/zswap.c >>>>> >>>>> diff --git a/mm/Kconfig b/mm/Kconfig >>>>> index 278e3ab..14b9acb 100644 >>>>> --- a/mm/Kconfig >>>>> +++ b/mm/Kconfig >>>>> @@ -446,3 +446,18 @@ config FRONTSWAP >>>>> and swap data is stored as normal on the matching swap device. >>>>> >>>>> If unsure, say Y to enable frontswap. >>>>> + >>>>> +config ZSWAP >>>>> + bool "In-kernel swap page compression" >>>>> + depends on FRONTSWAP && CRYPTO >>>>> + select CRYPTO_LZO >>>>> + select ZSMALLOC >>>> >>>> Again, I'm asking why zswap should have a dependent on CRPYTO? >>>> Couldn't we support it as a option? I'd like to use zswap without CRYPTO >>>> like zram. >>> >>> The reason we need CRYPTO is that zswap uses it to support a pluggable >>> compression model. zswap can use any compressor that has a crypto API >>> driver. zswap has _symbol dependencies_ on CRYPTO. If it isn't >>> selected, the build breaks. >> >> I think we can factor out compressoin part and remove dependency >> at compile time by Kconfig. No? > > I'm still not following. How would one "factor out" the crypto API > dependency when we use it to access the compressor modules. > > The only thing I can think you're saying is to hack up the code with > ifdefs to call the lzo code directly based on a Kconfig option. I > really hope you aren't saying that though :-/ Looking into this more, I found out that INET also selects CRYPTO, so unless the kernel is not doing networking, CRYPTO will be enabled anyway. EXT4 also selects it. > >> Of course, if we disable CRYPTO in Kconfig, >> we lost pluggable model but not a problem for embedded system. > > The pluggable model is _very_ necessary for us because we use it to > access our hardware compression accelerator. We do not use lzo in > that case. We use 842 (crypto/842.c and drivers/crypto/nx/nx-842.c). > > I'm not sure why we are misunderstanding on this. Is there a specific > objection to depending the crypto API here? I understand that you are > thinking about embedded systems. Does the enabling CRYPTO and > CRYPTO_LZO add significant size to the kernel or something? If size is the concern, I did a quick size diff between a vmlinux with and without CRYPTO: text data bss dec CRYPTO=n 4747622 602704 7774208 13124534 CRYPTO=y 4755437 602960 7774208 13132605 diff 7815 256 0 8071 Bottom line is CRYPTO adds about 8k to vmlinux. Thanks, Seth >Just trying to understand why this is a problem. > > Thanks, > Seth > >> >> Anyway, If it's a burden for you at a moment, I'm not going to insist on it. >> Will do it for myself. > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>