Messages in this thread |  | | Date | Thu, 13 Feb 2014 12:37:22 +0530 | From | Raghavendra K T <> | Subject | Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages |
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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 ?
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