Hi Jens, On Mon, Aug 14, 2017 at 10:17:09AM -0600, Jens Axboe wrote: > On 08/14/2017 09:38 AM, Jens Axboe wrote: > > On 08/14/2017 09:31 AM, Minchan Kim wrote: > >>> Secondly, generally you don't have slow devices and fast devices > >>> intermingled when running workloads. That's the rare case. > >> > >> Not true. zRam is really popular swap for embedded devices where > >> one of low cost product has a really poor slow nand compared to > >> lz4/lzo [de]comression. > > > > I guess that's true for some cases. But as I said earlier, the recycling > > really doesn't care about this at all. They can happily coexist, and not > > step on each others toes. > > Dusted it off, result is here against -rc5: > > http://git.kernel.dk/cgit/linux-block/log/?h=cpu-alloc-cache > > I'd like to split the amount of units we cache and the amount of units > we free, right now they are both CPU_ALLOC_CACHE_SIZE. This means that > once we hit that count, we free all of the, and then store the one we > were asked to free. That always keeps 1 local, but maybe it'd make more > sense to cache just free CPU_ALLOC_CACHE_SIZE/2 (or something like that) > so that we retain more than 1 per cpu in case and app preempts when > sleeping for IO and the new task on that CPU then issues IO as well. > Probably minor. > > Ran a quick test on nullb0 with 32 sync readers. The test was O_DIRECT > on the block device, so I disabled the __blkdev_direct_IO_simple() > bypass. With the above branch, we get ~18.0M IOPS, and without we get > ~14M IOPS. Both ran with iostats disabled, to avoid any interference > from that. Looks promising. If recycling bio works well enough, I think we don't need to introduce new split in the path for on-stack bio. I will test your version on zram-swap! Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
