Messages in this thread |  | | | Date | Thu, 2 Jul 2009 20:41:28 +0800 | | From | Wu Fengguang <> | | Subject | Re: fio mmap sequential read 30% regression |
On Thu, Jul 02, 2009 at 04:01:22PM +0800, Zhang, Yanmin wrote: > Comapring with 2.6.30's result, fio mmap sequtial read has > about 30% regression on one of my stoakley machine with 1 > JBOD (7 SAS disks) with kernel 2.6.31-rc1. > > Every disk has 2 partitions and 4 1-GB files per partition. Start > 10 processes per disk to do mmap read sequentinally. > > Bisect down to below patch. > > ef00e08e26dd5d84271ef706262506b82195e752 is first bad commit > commit ef00e08e26dd5d84271ef706262506b82195e752 > Author: Linus Torvalds <torvalds@linux-foundation.org> > Date: Tue Jun 16 15:31:25 2009 -0700 > > readahead: clean up and simplify the code for filemap page fault readahead > > This shouldn't really change behavior all that much, but the single rather > complex function with read-ahead inside a loop etc is broken up into more > manageable pieces. > > The behaviour is also less subtle, with the read-ahead being done up-front > rather than inside some subtle loop and thus avoiding the now unnecessary > extra state variables (ie "did_readaround" is gone). > > Fengguang: the code split in fact fixed a bug reported by Pavel Levshin: > the PGMAJFAULT accounting used to be bypassed when MADV_RANDOM is set, in > which case the original code will directly jump to no_cached_page reading. > > > The bisect is stable.
Let me take care of this bug: it may well be caused by my other readahead patches.
Thanks, Fengguang
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