Messages in this thread | | | Date | Tue, 11 Mar 2003 12:43:12 -0800 | From | Ross Biro <> | Subject | Re: out_of_memory called to often |
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Jason Li wrote:
>Hi, > >We are running an embedded linux (2.4.19) with no swap >sapce. And we haven't applied any rmap yet. > I believe you may be seeing the same issue I brought up in a previous email. Have you tried what I suggested? I've appended the email to this message with out the test code.
Ross
I've verified this in 2.4.21-pre5 by code inspection and can trigger the problem on 2.4.18. It appears to have been fixed in 2.5.
The folowing code vmscan.c assumes that there is available swap space.
/* * this is the non-racy check for busy page. */ if (!page->mapping || !is_page_cache_freeable(page)) { spin_unlock(&pagecache_lock); UnlockPage(page); page_mapped: if (--max_mapped >= 0) continue;
/* * Alert! We've found too many mapped pages on the * inactive list, so we start swapping out now! */ spin_unlock(&pagemap_lru_lock); swap_out(priority, gfp_mask, classzone); return nr_pages; }
If there is no swap space, then unfreeable pages are left on the inactive queue and the vmtree is walked rather than going through the rest of the inactive queue. I believe something like /* * this is the non-racy check for busy page. */ if (!page->mapping || !is_page_cache_freeable(page)) { spin_unlock(&pagecache_lock); UnlockPage(page); page_mapped: /* If we don't have any swap space left, there is no reason to worry about pages that do not have swap associated with them, there is nothing we can do about it. */ if (!page->mapping && !swap_avail()) { /* Let's make the page active since we cannot swap it out. It get's it off the inactive list. */ spin_unlock(&pagemap_lru_lock); activate_page(page); ClearPageReferenced(page); spin_lock(&pagemap_lru_lock); continue; } if (--max_mapped >= 0) continue;
/* * Alert! We've found too many mapped pages on the * inactive list, so we start swapping out now! */ spin_unlock(&pagemap_lru_lock); swap_out(priority, gfp_mask, classzone); return nr_pages; }
will work better when there is no swap space available. If this change is made, it may also be necessary to limit refill_inactive to prevent it from using too much cpu. This bug can be triggered with the attached code and the correct parameters. In particular on a 3 gigabyte machine with no swap,
for i in $(seq 0 9); do dd if=/dev/zero of=file$i bs=1024k count=512; done killmm 1032735283 2 9
Usually causes an out of memory error when there is hundreds of megabytes of cache.
Ross
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