From: Hanna Linder <hannal@us...> - 2002-07-11 19:06:09
It has been a long time since we all talked. Let's have
our regularly scheduled LSE Conference Call Tomorrow at
9:30am PST, 12:30pm EST. The phone numbers are on the
lse sourceforge home page at: http://lse.sf.net/mtg
Some items that have been discussed on the mailing list
1. rwhron publishing lmbench results between -jam and -aa
kernel Pipe AF/Unix
----------------- ------- -------
2.4.19-pre10-aa4 33.941 70.216
2.4.19-pre10-jam2 7.877 16.699
3. Mingming Cao published a patch on breaking up the global
lock on IPC mechanisms:
Currently the use of three type of IPC resources(semaphores, message
queues and shared memory segments) are synchronized by three global
locks respectively. This means, for example, all semaphores are going
to share one global lock. Although the IPC locks are not highly used as
the BKL, on some applications which use lots of IPC resources(e.g. IPC
semaphores), there could be contention.
It makes more sense to me if we break the one globale lock for all
semaphores into one lock per sempahore id(same for message queue
id/shared memory id). I attached a patch which implements this idea.
Just sharing my thoughts with you. Please send any of your comments to
3. Dipankar Sarma published results of RCU overhead whith
Based on these measurements, we can draw the following conclusions -
1. RCU, implemented the right way, can be beneficial even when
updates are more than rare. Atleast one patch (rcu_ltimer) shows
a net improvement (gain in ip_route_output_key - rcu overhead) under
heavy update load.
2. When updates are rare most implementations can work well and show
3. Global queues are out, it is important to have per-cpu queues as
seen from overheads in rcu_poll code.
4. Global atomic RCU counter in rcu_sched probably hurts as seen
in call_rcu() overhead. So we should try to avoid such global
4. dbench results from Andrew Mortens kmap patches
5. Hubertus Franke's GCOV toolset update
6. Adam Litke merging gcov, kernprof and lockmeter
If you would like to discuss any of these then please attend.
If there is anything else you would like to discuss bring it up
at the meeting tomorrow.
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