On 12/01/2010 06:33 PM, Anthony Liguori wrote:
BTW, by this logic, even a 1-byte dirty bitmap is only 16mb which can
be read in less than 16ms so where is the reported 24 minute stall
coming from?
a) we read the bitmap more than once
Not in a single iteration which is what the "stall" would consist of.
b) the 1ms is based on "we read" it with longs and optimized, just now
we have to read it by byte and inside the byte.
Byte accesses verse long access doesn't turn 16ms into 24 minutes.
We need actual measurements instead of speculations. Walking the dirty
bitmap _did_ _not_ introduce any stalls. It was the qemu mutex, or
walking kvm data structures in the kernel, or something. No amount of
dirty bitmap optimization will fix it.
--
error compiling committee.c: too many arguments to function
