On 1/10/13 2:38 AM, Konstantin Belousov wrote:
On Thu, Jan 10, 2013 at 01:56:48AM -0500, Alfred Perlstein wrote:
Here are more convenient links that give diffs against FreeBSD and
jemalloc for the proposed changes:
FreeBSD:
https://github.com/alfredperlstein/freebsd/compare/13e7228d5b83c8fcfc63a0803a374212018f6b68~1...utrace2
Why do you need to expedite the records through the ktrace at all ?
Wouldn't direct write(2)s to a file allow for better performance
due to not stressing kernel memory allocator and single writing thread ?
Also, the malloc coupling to the single-system interface would be
prevented.
I believe that other usermode tracers also behave in the similar way,
using writes and not private kernel interface.
Also, what /proc issues did you mentioned ? There is
sysctl kern.proc.vmmap which is much more convenient than /proc/pid/map
and does not require /proc mounted.
jemalloc:
https://github.com/alfredperlstein/jemalloc/compare/master...utrace2
Konstantin, you are right, it is a strange thing this utrace. I am not
sure why it was done this way.
You are correct in that much more efficient system could be made using
writes gathered into a single write(2).
Do you think there is any reason they may have re-used the kernel paths
for ktrace even at the cost of efficiency?
About kern.proc.vmmap I will look into that.
-Alfred
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