On 2013-06-12 12:22 AM, John Stultz wrote:
From: Minchan Kim <minchan@xxxxxxxxxx> This patch adds new system call sys_vrange. NAME vrange - Mark or unmark range of memory as volatile SYNOPSIS int vrange(unsigned_long start, size_t length, int mode, int *purged); DESCRIPTION Applications can use vrange(2) to advise the kernel how it should handle paging I/O in this VM area. The idea is to help the kernel discard pages of vrange instead of reclaiming when memory pressure happens. It means kernel doesn't discard any pages of vrange if there is no memory pressure. mode: VRANGE_VOLATILE hint to kernel so VM can discard in vrange pages when memory pressure happens. VRANGE_NONVOLATILE hint to kernel so VM doesn't discard vrange pages any more. If user try to access purged memory without VRANGE_NOVOLATILE call, he can encounter SIGBUS if the page was discarded by kernel.
I wonder if it would be possible to provide additional information here, for example "purge range at a time" as opposed to "purge page at a time". There are some valid use cases for both approaches and it doesn't make sense to deny one use case.
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