Hello Hugh, Izik For the MADV_MERGEABLE + MADV_UNMERGEABLE changes added in 2.6.32, I've written the following man-pages text. Could you please review/fix/ACK. Thanks to Andi and Andrew for pointers that this documentation was needed. Thanks, Michael --- a/man2/madvise.2 +++ b/man2/madvise.2 @@ -156,6 +157,42 @@ and the page being unmapped. This feature is intended for memory testing. This feature is only available if the kernel was configured with .BR CONFIG_MEMORY_FAILURE . +.TP +.BR MADV_MERGEABLE " (since Linux 2.6.32)" +Enable Kernel Samepage Merging (KSM) for the pages in the range specified by +.I addr +and +.IR len . +The KSM daemon +.RI ( ksmd ) +periodically scans those areas of user memory that have +been marked as mergeable, +looking for pages with identical content. +These are replaced by a single write-protected page (which is automatically +copied if a process later wants to update the content of the page). +KSM only merges private anonymous pages (see +.BR mmap (2)). +The KSM feature is intended for applications that generate many +instances of the same data (e.g., virtualization systems such as KVM). +It can consume a lot of processing power; use with care. +See the kernel source file +.I Documentation/vm/ksm.txt +for more details. +The +.BR MADV_MERGEABLE +and +.BR MADV_UNMERGEABLE +operations are only available if the kernel was configured with +.BR CONFIG_KSM. +.TP +.BR MADV_UNMERGEABLE " (since Linux 2.6.32)" +Undo the effect of an earlier +.BR MADV_MERGEABLE +operation on the specified address range; +KSM unmerges whatever pages it had merged in the address rnage specified by +.IR addr +and +.IR length . .SH "RETURN VALUE" On success .BR madvise () @@ -189,6 +226,14 @@ is not a valid value .IP * The application is attempting to release locked or shared pages (with .BR MADV_DONTNEED ). +.IP * +.BR MADV_MERGEABLE +or +.BR MADV_UNMERGEABLE +was specified in +.IR advice , +but the kernel was not configured with +.BR CONFIG_KSM . .RE .TP .B EIO @@ -221,8 +266,10 @@ for file access. .BR MADV_REMOVE , .BR MADV_DONTFORK , .BR MADV_DOFORK , +.BR MAD_HWPOISON , +.BR MADVISE_MERGEABLE , and -.BR MAD_HWPOISON +.BR MADVISE_UNMERGEABLE are Linux-specific. .SH NOTES .SS "Linux Notes" -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
