Linus Torvalds <torvalds@transmeta.com> writes:
> On 25 Oct 2001, Zlatko Calusic wrote:
> >
> > Yes, I definitely have DMA turned ON. All parameters are OK. :)
>
> I suspect it may just be that "queue_nr_requests"/"batch_count" is
> different in -ac: what happens if you tweak them to the same values?
>
> (See drivers/block/ll_rw_block.c)
>
> I think -ac made the queues a bit deeper the regular kernel does 128
> requests and a batch-count of 16, I _think_ -ac does something like "2
> requests per megabyte" and batch_count=32, so if you have 512MB you should
> try with
>
> queue_nr_requests = 1024
> batch_count = 32
>
> Does that help?
>
Unfortunately not. It makes a machine quite unresponsive while it's
writing to disk, and vmstat 1 discovers strange "spiky"
behaviour. Average throughput is ~ 8MB/s (disk is capable of ~ 13MB/s)
procs memory swap io system cpu
r b w swpd free buff cache si so bi bo in cs us sy id
2 0 0 0 3840 528 441900 0 0 0 34816 188 594 2 34 64
0 1 0 0 3332 536 442384 0 0 4 10624 187 519 2 8 90
0 1 0 0 3324 536 442384 0 0 0 0 182 499 0 0 100
2 1 0 0 3300 536 442384 0 0 0 0 198 486 0 1 99
1 1 0 0 3304 536 442384 0 0 0 0 186 513 0 0 100
0 1 1 0 3304 536 442384 0 0 0 0 193 473 0 1 99
0 1 1 0 3304 536 442384 0 0 0 0 191 508 1 1 98
0 1 0 0 3884 536 441840 0 0 4 44672 189 590 4 40 56
0 1 0 0 3860 536 441840 0 0 0 0 186 526 0 1 99
0 1 0 0 3852 536 441840 0 0 0 0 191 500 0 0 100
0 1 0 0 3844 536 441840 0 0 0 0 193 482 1 0 99
0 1 0 0 3844 536 441840 0 0 0 0 187 511 0 1 99
0 2 1 0 3832 540 441844 0 0 4 0 305 1004 3 2 95
0 3 1 0 3824 544 441844 0 0 4 0 410 1340 2 2 96
0 3 0 0 3764 552 441916 0 0 12 47360 346 915 6 41 53
0 3 0 0 3764 552 441916 0 0 0 0 373 887 0 0 100
0 3 0 0 3764 552 441916 0 0 0 0 278 692 1 2 97
1 3 0 0 3764 552 441916 0 0 0 0 221 579 0 3 97
0 3 0 0 3764 552 441916 0 0 0 0 286 704 0 2 98
I'll now test "batch_count = queue_nr_requests / 3", which I found in
2.4.14-pre2, but with queue_nr_request still left at 1024. And report
results after that.
-- Zlatko - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Wed Oct 31 2001 - 21:00:30 EST