Questions about /proc/stat

[M. Edward]

I have some questions about the "page" and "swap" entries in /proc/stat.
Here is the relevant code from 2.4.12
/usr/src/linux/fs/proc/proc_misc.c:

    292         len += sprintf(page + len,
    293                 "page %u %u\n"
    294                 "swap %u %u\n"
    295                 "intr %u",
    296                         kstat.pgpgin >> 1,
    297                         kstat.pgpgout >> 1,
    298                         kstat.pswpin,
    299                         kstat.pswpout,
    300                         sum
    301         );

1. Why are kstat.pgpgin and kstat.pgpgout shifted right / halved?

2. Are the "page" and "swap" numbers mutually exclusive? That is, if a
page is brought in from swap and counted in kstat.pswpin, is it also
counted in kstat.pgpgin? I found the places in the code where the counts
are incremented, but I couldn't tell if the swapin routine calls the
block driver or not.
--
M. Edward Borasky

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