glibtop_get_proc_mem
libgtop has a function glibtop_get_proc_mem to retrieve basic memory usage of a process. It fills a struct glibtop_proc_mem which looks like:
struct _glibtop_proc_mem
{
guint64 flags;
guint64 size;
guint64 vsize;
guint64 resident;
guint64 share;
guint64 rss;
guint64 rss_rlim;
};
Yes, size/vsize and resident/rss look like duplicate. At least on the linux implementation, even if size/vsize and resident/rss come from /proc/self/stat and /proc/self/statm, you can see in linux/fs/proc/{array,task_mmu}.c that they have the same values. So, it seems to me that the only unique members of struct glibtop_proc_mem are size, resident and share (ok there are also flags which flags which members are filled and rss_lim).
linux proportional set size
Linux 2.6.25 comes with a new stat in /proc/self/smaps called pss which is even smarter/accurate than private_dirty. There's glibtop_get_proc_map which currently have all the smaps member but not this new pss. So what is the smarter way to get this new pss in libgtop without breaking everything ?
- break the ABI ?
I could simply extend struct glibtop_proc_map. That would break the ABI, which i'm allowed to because libgtop is desktop. But that's bad practice since packagers have to rebuild everything. That's a painful migration that may delay the adoption of newer versions of the library.
- break the API ?
What about cleaning up the glibtop_proc_mem duplicate members, mark unused some of them and rename rss to pss while keeping it binary compatible ? That would make the API a bit more sensible. I've scanned the Debian/unstable archive and that would break the build 3-6 packages but i would be able to submit trivial patches to fix glibtop_get_proc_mem usage. (And also add glibtop_init(); which are missing everywhere).
- hide pss inside rss ?
So what's best ?
is great to find bugs with patches but it doesn't help to find "Accepted Commit-Now" patches. There was for a long time a kFreeBSD patch for libgtop on bugzilla, i tagged it "Accepted Commit-Now" but it was never commited and i forgot about it. But last week, i got a new patch from Debian adding kFreeBSD support and commited it, then i found the old patch. What a waste of work :/