Messages in this thread Patch in this message | | | Date | Fri, 14 Jun 2002 16:32:31 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] 2.5.21 IDE 91 |
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"Hron, Randall" wrote: > > > (lord knows i'm trying to get up to speed), but, in the meantime, I can > > test the crap out of a kernel :). > > tiobench is having trouble completing in kernels >= 2.5.19 on my K6-2 > 384 mb ram, IDE test system. The parameters I'm using are: > > tiobench.pl --size 2048 --numruns 3 --threads 1 --threads 32 --threads 64 > --threads 128 > > --size depends on ram and disk space. > > Early in 2.5, dbench 192 would exercise a bug or two. > (requires about 5GB of disk space) > > Linux Test Project's runalltests.sh has occasionally triggered a bug.
Is this still happening? What was the bug?
> 2.5 took a drop in dbench throughput recently. > > dbench ext2 128 processes Average High Low(MB/sec)
Is this still with 384 megs of memory?
> 2.5.19 18.60 21.69 14.58 > 2.5.20 12.89 13.15 12.79 > 2.5.21 12.67 12.94 12.51 >
One possibile culprit here is the doubling of the request queue size in 2.5.20. A long time ago it was 1024 slots. Then it went to 128. That's where it is in Marcelo kernels. Then -ac kernels went up to 1024 because they have read-latency2. Somehow 2.5 found itself at 256 slots. In 2.5.20 it slealthily snuck up to 512 slots. I didn't squeak about this because I was interested to see what effect it would have.
Does this patch get the throughput back?
Index: drivers/block/ll_rw_blk.c =================================================================== RCS file: /opt/cvs/lk/drivers/block/ll_rw_blk.c,v retrieving revision 1.66 diff -u -r1.66 ll_rw_blk.c --- drivers/block/ll_rw_blk.c 9 Jun 2002 07:13:15 -0000 1.66 +++ drivers/block/ll_rw_blk.c 14 Jun 2002 23:35:54 -0000 @@ -1974,6 +1974,8 @@ if (queue_nr_requests > 512) queue_nr_requests = 512; + queue_nr_requests = 256; + /* * Batch frees according to queue length */
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