"Jeff V. Merkey" <jmerkey@timpanogas.com> writes:
> If I increase the size of the LRU in NWFS to a size above 3000 buffers,
> Linux starts getting SLOWER .... SLOOOWWWWWWERRRR......
> SLOOOOOOOWWWWWWEEEERR ..... which is counter intuitive since more cache
> should get faster performance. The performance degredation as I
> increase the LRU in size is @ log2N, which would seem to indicate that
> somewhere down inside of linux, as some linked lists start getting
> longer, Linux really bogs down and exhibits asymtopic behavior.
The culprit is probably the elevator code in ll_rw_blk, which uses
a single linked list, and possible the related queue walking code in
the SCSI driver. These queues are walked all the time to coalesce read/write
requests. You can check by booting with profile=2
and then using /usr/sbin/readprofile to get profile logs. The bad
routine should clearly show off.
-Andi
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This archive was generated by hypermail 2b29 : Sat Apr 15 2000 - 21:00:15 EST