rate limit calls to posix_fadvise() #145
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There can be a large kernel overhead involved in POSIX_FADV_DONTNEED.
There is no point in calling this per item logged, so rate limit
to at most once per 2MiB written.
With a simple test program that logs 100K items at WARNING level:
Before:
$ time strace -c -e fadvise64 log.test \
-log_dir=/dev/shm -logtofiles=true -logtostderr=false
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00 12.522509 125 99957 fadvise64
------ ----------- ----------- --------- --------- ----------------
real 0m52.671s
user 0m2.194s
sys 0m44.022s
After:
$ time strace -c -e fadvise64 log.test \
-log_dir=/dev/shm -logtofiles=true -logtostderr=false
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00 0.000759 152 5 fadvise64
------ ----------- ----------- --------- --------- ----------------
real 0m4.206s
user 0m1.436s
sys 0m3.153s
Fixes issue #84
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Sep 2, 2019
rate limit calls to posix_fadvise()
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There can be a large kernel overhead involved in POSIX_FADV_DONTNEED.
There is no point in calling this per item logged, so rate limit
to at most once per 2MiB written.
With a simple test program that logs 100K items at WARNING level:
Before:
$ time strace -c -e fadvise64 log.test
-log_dir=/dev/shm -logtofiles=true -logtostderr=false
% time seconds usecs/call calls errors syscall
100.00 12.522509 125 99957 fadvise64
real 0m52.671s
user 0m2.194s
sys 0m44.022s
After:
$ time strace -c -e fadvise64 log.test
-log_dir=/dev/shm -logtofiles=true -logtostderr=false
% time seconds usecs/call calls errors syscall
100.00 0.000759 152 5 fadvise64
real 0m4.206s
user 0m1.436s
sys 0m3.153s
Fixes issue #84