Andreas Hirstius wrote on Wednesday, April 06, 2005 1:33 AM > The problems mentioned in this discussion about the Fusion-MPT I can > perfectly reproduce on my boxes with 2.6.11, but only with pages sizes > 4k and 8k; > With 16k and 64k pages I don't see any problem at all !!! > Actually I see block size <-> page size correlations which are similiar > to the correlations I see in my setup... > i.e. 2.6.11 and 4k pages: > dd ...bs=4096: 40MB/s > dd ...bs=8192: 74MB/s > > i.e. 2.6.11 and 8k pages: > dd ...bs=8192: 56MB/s > dd ...bs=16384: 74MB/s
It is very odd. I think it has something to do with generic file read ahead logic. The read ahead window did not push far enough to keep the disk busy. Some of the size calculation are in unit of page, so smaller page size will have smaller effective read ahead size. Try look into mm/readahead.c. I bet you can find the answer to your performance problem there. If not, then I guess we have to keep on looking ;-) - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
