Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [RFC 1/3] /dev/low_mem_notify | Date | Tue, 24 Jan 2012 16:22:36 +0000 |
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On Wednesday 18 January 2012, Pekka Enberg wrote: > >> +struct vmnotify_event { > >> + /* Size of the struct for ABI extensibility. */ > >> + __u32 size; > >> + > >> + __u64 nr_avail_pages; > >> + > >> + __u64 nr_swap_pages; > >> + > >> + __u64 nr_free_pages; > >> +}; > > > > Two fields here most likely session-constant, (nr_avail_pages and > > nr_swap_pages), seems not much sense to report them in every event. If we > > have memory/swap hotplug user-space can use sysinfo() call. > > I actually changed the ABI to look like this: > > struct vmnotify_event { > /* > * Size of the struct for ABI extensibility. > */ > __u32 size; > > __u64 attrs; > > __u64 attr_values[]; > }; > > So userspace can decide which fields to include in notifications.
Please make the first member a __u64 instead of a __u32. This will avoid incompatibility between 32 and 64 bit processes, which have different alignment rules on x86: x86-32 would implicitly pack the struct while x86-64 would add padding with your layout.
Arnd
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