Phil Carns wrote:
Yeah that is odd. Setting the cursor for each call to
iterate_handles may be the reason for it starting over. Do you know
how many times it starts over? The number of times iterate_handles
is called will be (# of files / 4096).
It only goes through the file twice if I am looking at the log
correctly. Also, I just realized that on both passes (the one jumping
backwards 40KB at a time and the one jumping backwards 4KB at a time) it
is only reading 4KB per pread. I don't know what it is doing from a db
point of view, but from an access point of view it looks like it goes
backwards with a strided pattern and then goes backwards reading the
entire thing. There are some other reads scattered here and there, but
those two cycles represent the overwhelming majority of the total preads
in the strace file. By spot checking I don't really see any significant
divergence from the patterns.
It also just occurred to me that maybe I should repeat the strace and
try to capture it with timestamps; I'm not really sure if both of these
pread cycles are actually during the scan or not.
I just double checked- both of those big pread cycles are happening
after this message is logged:
[D 13:06:53.916769] dbpf collection 752900094 - Setting collection
handle ranges to 4-536870914,4294967292-4831838202
... but before the next message. So they do appear to both be a result
of the handle scanning on startup.
-Phil
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