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To: Linus Torvalds <torvalds@transmeta.com>
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Subject: Re: xmm2 - monitor Linux MM active/inactive lists graphically
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Reply-To: zlatko.calusic@iskon.hr
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From: Zlatko Calusic <zlatko.calusic@iskon.hr>
Date: 26 Oct 2001 11:45:55 +0200
In-Reply-To: <Pine.LNX.4.31.0110250920270.2184-100000@cesium.transmeta.com> (Linus Torvalds's message of "Thu, 25 Oct 2001 09:31:12 -0700 (PDT)")
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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
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