On 2010-10-01 04:30, Malahal Naineni wrote: > Jens Axboe [jaxboe@xxxxxxxxxxxx] wrote: >> On 2010-09-24 21:20, Malahal Naineni wrote: >>> Jens Axboe [jaxboe@xxxxxxxxxxxx] wrote: >>>>> This patch also _fixed_ our problem. So we are fine with either patch, >>>>> but this patch is preferred as it enables more request merges. Also, >>>>> both patches maybe needed for some configurations. >>>> >>>> Plus it doesn't needlessly bounce, that's the real problem you want to >>>> fix. I have applied this thread patch to for-2.6.37/core, thanks. >>> >>> There is a shortcut check in blk_queue_bounce() that uses blk_max_pfn to >>> return without doing anything. blk_max_pfn is not updated when we do >>> hot-plug memory add, so bounce buffers are NOT really used in our case >>> (thankfully)! >> >> Any reason we can't just add a hot mem add notifier and update the block >> copies when we need to? > > Actually it is quite simple, but power arch guys decided not to update > max_pfn and max_low_pfn when someone adds or removes memory. They do > seem to indicate that it is not an over sight! On the other hand, x86 > arch does update those. > > Another approach would be defining max_possible_pfn (maximum allowable > memory) which would be constant (based on architecture) and hopefully > adapters that we care still take the short-cut. > > Also, this patch broke some USB hosts. Can you please back out this > patch and apply the one below instead: > > http://thread.gmane.org/gmane.linux.kernel.next/14158 Done, thanks. -- Jens Axboe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
