>>> On 3/10/2016 at 01:25 PM, Christer Solskogen <[email protected]> wrote: > This is a bit more technical: https://lwn.net/Articles/537422/
Based on the lead-in to the article, this was intended for systems where CPU and RAM are cheap, and I/O is very expensive. For the mainframe, neither CPU nor RAM are cheap, but the I/O is quite a bit less expensive than on other architectures. I suppose support for the zEDC hardware compression feature would reduce some of the CPU expended for compression. > I wouldn't say experimental anymore, since it's been in the kernel since > 3.7. The kernel developers themselves have flagged it that way: Compressed cache for swap pages (EXPERIMENTAL) > The reason I'm asking is that on x86_64 is enabled on Ubuntu like this: > CONFIG_ZSWAP=y > > While on SLES11 and SLES12 on s390x CONFIG_ZSWAP isn't even mentioned, > so at first it didn't even look like ZSWAP is available at all on > s390x. > If the module was available, but not compiled in it would look > something like this: #CONFIG_ZSWAP is not set Since this was introduced with 3.7, it would only be available on SLES11 if there had been a feature request to back port it to the 3.0.101 kernel in use. The ZSWAP feature depends on FRONTSWAP being configured. For SLES12, we don't enable the FRONTSWAP feature on s390x, which means that the ZSWAP feature isn't even presented as an option. The fact that both FRONTSWAP and ZSWAP are configured on x86_64 tells me that there was a conscious decision made to exclude it on s390x. If you believe you have a business need for this feature, you should talk to your sales rep. or technical sales support rep. to get a feature request entered for that. Mark Post ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
