Re: Patch for block write clustering

Emil Briggs (
Thu, 5 Mar 1998 01:29:56 -0500 (EST)

>> Yes, I started looking through the lower-level code. I am puzzled though
>> as to why the low-level sorting doesn't seem to have much effect in 2.0.33
>> at least. Using a stock 2.0.33 kernel with write-caching turned off on the
>> drive itself causes a huge performance hit. (I can post the benchmark program
>> I used if anyone wants to try it themselves)
>One new 2.1.x function in the sort code is attempt_merge() in
>drivers/block/ll_rw_blk.c. I doubt that it accounts for the difference,
>but perhaps -- we can try adding a printk() to that function, and verifying
>whether it is called frequently under the benchmark.

Thanks. I'll put some printk's in 2.0.33 and 2.1.xx and see if I can
figure out what's going on. From your other note about the request
queues I think I'll try some tests that access multiple partitions
at the same time and see how that works.


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