Messages in this thread | | | From | David Woodhouse <> | Subject | Block device request merging - repeated requests. | Date | Mon, 31 Jan 2000 14:12:54 +0000 |
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I'm playing with a new block device driver in 2.3.41
When I try something simple like 'dd if=/dev/zero of=/dev/mydevice bs=512 count=10'
... I find that the requests are helpfully merged.
Unfortunately, I find that they're also repeated.
So - what was ten separate write requests, for each consecutive block, now becomes ten write requests, each for the whole ten.
Am I doing something wrong - when I'm passed a request should I be checking it to see if it's already uptodate?
Or is the block request combining code in 2.3.41 completely shagged?
# dd if=nftl.c of=/dev/nftla bs=512 count=2 2+0 records in 2+0 records out
NFTL_open called NFTL write request of 0x2 sectors @ 0 Writing block 0 to EUN 5f Writing block 1 to EUN 5a NFTL write request completed OK NFTL write request of 0x2 sectors @ 0 Writing block 0 to EUN 60 Writing block 1 to EUN 5b NFTL write request completed OK
By setting max_sectors to 1 for the device in question, effectively disabling the request merging, I return the system to sane behaviour.
-- dwmw2
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