On Fri, 6 Apr 2012, Nikola Ciprich wrote: > Hi, sorry it took me a bit longer. > > here's my backport,
To 3.0.27 I presume; I've not tried it against 3.2.14, haven't checked if that would be much the same or not. > compiles fine, kernel boots without any problems. > please review. Thank you for doing the work, but I'm afraid it looks wrong to me. I'd be more confident to leave it to Mel myself. Comments below. > n. > > Signed-off-by: Nikola Ciprich <[email protected] > > (backport of upstream commit cc715d99e529d470dde2f33a6614f255adea71f3) > > mm: vmscan: forcibly scan highmem if there are too many buffer_heads > pinning highmem > > Stuart Foster reported on bugzilla that copying large amounts of data > from NTFS caused an OOM kill on 32-bit X86 with 16G of memory. Andrew > Morton correctly identified that the problem was NTFS was using 512 > blocks meaning each page had 8 buffer_heads in low memory pinning it. > > In the past, direct reclaim used to scan highmem even if the allocating > process did not specify __GFP_HIGHMEM but not any more. kswapd no longer > will reclaim from zones that are above the high watermark. The intention > in both cases was to minimise unnecessary reclaim. The downside is on > machines with large amounts of highmem that lowmem can be fully consumed > by buffer_heads with nothing trying to free them. > > The following patch is based on a suggestion by Andrew Morton to extend > the buffer_heads_over_limit case to force kswapd and direct reclaim to > scan the highmem zone regardless of the allocation request or watermarks. > > Addresses https://bugzilla.kernel.org/show_bug.cgi?id=42578 > > --- > > diff -Naur linux-3.0/mm/vmscan.c > linux-3.0-cc715d99e529d470dde2f33a6614f255adea71f3-backport/mm/vmscan.c > --- linux-3.0/mm/vmscan.c 2012-04-05 23:09:28.364000004 +0200 > +++ linux-3.0-cc715d99e529d470dde2f33a6614f255adea71f3-backport/mm/vmscan.c > 2012-04-05 23:25:30.989968627 +0200 > @@ -1581,6 +1581,14 @@ diff -p is often more helpful, and especially so for this patch: here we are in shrink_active_list(). > putback_lru_page(page); > continue; > } > + > + if (unlikely(buffer_heads_over_limit)) { > + if (page_has_private(page) && trylock_page(page)) { > + if (page_has_private(page)) > + try_to_release_page(page, 0); > + unlock_page(page); > + } > + } > > if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { > nr_rotated += hpage_nr_pages(page); I don't think this does functional harm, but it duplicates the work done by the pagevec_strip() you left in move_active_pages_to_lru(), so the resulting source would be puzzling. We could remove the pagevec_strip(), but really, it was just a misunderstanding that led to my little buffer_heads_over_limit cleanup in one place getting merged in with Mel's significant buffer_heads_over_limit fix in another. My cleanup doesn't deserve backporting to 3.0 or 3.2: I included it in the 3.3 backport to avoid raised eyebrows, but once we get back to kernels with pagevec_strip(), let's just leave this hunk out. > @@ -2053,6 +2061,14 @@ Here we are in all_unreclaimable(). > struct zoneref *z; > struct zone *zone; > > + /* > + * If the number of buffer_heads in the machine exceeds the maximum > + * allowed level, force direct reclaim to scan the highmem zone as > + * highmem pages could be pinning lowmem pages storing buffer_heads > + */ > + if (buffer_heads_over_limit) > + sc->gfp_mask |= __GFP_HIGHMEM; > + But in Mel's patch that belongs to shrink_zones(): I don't see a reason to move it in the backport. > for_each_zone_zonelist_nodemask(zone, z, zonelist, > gfp_zone(sc->gfp_mask), sc->nodemask) { > if (!populated_zone(zone)) > @@ -2514,7 +2530,8 @@ I think this hunk in balance_pgdat() is correct. > (zone->present_pages + > KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / > KSWAPD_ZONE_BALANCE_GAP_RATIO); > - if (!zone_watermark_ok_safe(zone, order, > + if ((buffer_heads_over_limit && is_highmem_idx(i)) || > + !zone_watermark_ok_safe(zone, order, > high_wmark_pages(zone) + balance_gap, > end_zone, 0)) { > shrink_zone(priority, zone, &sc); > @@ -2543,6 +2560,17 @@ But this hunk in balance_pgdat() comes too late: it should set end_zone in between the inactive_anon_is_low shrink_active_list and the !zone_watermark_ok_safe() setting of end_zone higher up, before the previous hunk. > continue; > } > > + /* > + * If the number of buffer_heads in the machine > + * exceeds the maximum allowed level and this node > + * has a highmem zone, force kswapd to reclaim from > + * it to relieve lowmem pressure. > + */ > + if (buffer_heads_over_limit && is_highmem_idx(i)) { > + end_zone = i; > + break; > + } > + > if (!zone_watermark_ok_safe(zone, order, > high_wmark_pages(zone), end_zone, 0)) { > all_zones_ok = 0; Hugh -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
