On 02/11/2014 03:05 AM, David Rientjes wrote:
On Mon, 10 Feb 2014, Raghavendra K T wrote:So I understood that you are suggesting implementations like below 1) I do not have problem with the below approach, I could post this in next version. ( But this did not include 4k limit Linus mentioned to apply) unsigned long max_sane_readahead(unsigned long nr) { unsigned long local_free_page; int nid; nid = numa_mem_id(); /* * We sanitize readahead size depending on free memory in * the local node. */ local_free_page = node_page_state(nid, NR_INACTIVE_FILE) + node_page_state(nid, NR_FREE_PAGES); return min(nr, local_free_page / 2); } 2) I did not go for below because Honza (Jan Kara) had some concerns for 4k limit for normal case, and since I am not the expert, I was waiting for opinions. unsigned long max_sane_readahead(unsigned long nr) { unsigned long local_free_page, sane_nr; int nid; nid = numa_mem_id(); /* limit the max readahead to 4k pages */ sane_nr = min(nr, MAX_REMOTE_READAHEAD); /* * We sanitize readahead size depending on free memory in * the local node. */ local_free_page = node_page_state(nid, NR_INACTIVE_FILE) + node_page_state(nid, NR_FREE_PAGES); return min(sane_nr, local_free_page / 2); }I have no opinion on the 4KB pages, either of the above is just fine.
I was able to test (1) implementation on the system where readahead problem occurred. Unfortunately it did not help.
Reason seem to be that CONFIG_HAVE_MEMORYLESS_NODES dependency of numa_mem_id(). The PPC machine I am facing problem has topology like this: numactl -H --------- available: 2 nodes (0-1) node 0 cpus: 0 1 2 3 4 5 6 7 12 13 14 15 16 17 18 19 20 21 22 23 24 25 ... node 0 size: 0 MB node 0 free: 0 MB node 1 cpus: 8 9 10 11 32 33 34 35 ... node 1 size: 8071 MB node 1 free: 2479 MB node distances: node 0 1 0: 10 20 1: 20 10 So it seems numa_mem_id() does not help for all the configs.. Am I missing something ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
